Is it necessary in order to denounce evil that it be removed completely, or is it sufficient to reduce it

The correct view is that we have to remove evil as much
as we can. Our efforts should be aimed primarily at removing it completely.
If we are not able to do that, but we can reduce it or reduce some of
its effects, then the basic principles of sharee’ah dictate that we
should do that, especially since we are living at a time when he evildoershave
the upper hand and those who seek to enjoin what is good and forbid
what is evil and to call people to Allaah are unable to achieve all
that they want to do. We can at least reduce the effects of evil; if
there is something that is difficult to remove, this is no excuse for
not doing what we can. We should not give up altogether on something
of which we can only do a part. Allaah does not burden any soul beyond
its scope, but we have to be certain about the basic principle in this
matter, which is that the daa’iyah (caller) who wants to enjoin what
is good and forbid what is evil should not be content with a partial
solution or accept a reduction of the evil when it is possible to eradicate
it completely. 

Often those who enjoin what is good and forbid what is
evil are content to reduce the evil without striving to remove it… Like
the one who tells a woman who is showing a lot of her charms to non-mahram
men to cover all of that apart from the hands and face, even though
he is able to tell her to observe complete hijaab.

 And like the one who passes by someone who is playing
singing and music loud, and he tells him to turn down the sound of that
evil. 

And like the one who is asked to teach women or girls,
and he sets down the condition that they should wear hijaab and not
speak in soft voices, even though he is able to demand that a screen
be placed between him and them so that they can hear his voice without
him seeing them. 

Among the evidence concerning this matter that is mentioned
in the Qur’aan is what Moosa (peace be upon him) did with the calf which
the Children of Israel worshipped and were devoted to. He said: 

“We will certainly burn it, and scatter its particles
in the sea”

[Ta-Ha 20:97 – interpretation of the meaning]

The Sunnah is what the Prophet

(peace and blessings of Allaah be upon him) did with the masjid al-diraar
(a mosque built by way of harming and diselief, cf. al-Tawbah 9:107),
which had been built by the hypocrites. He ordered that it should be
burned after being detsroyed. 

Al-Bukhaari and others narrated from the hadeeth of Ibn
Mas’ood (may Allaah be pleased with him) that he said, “The Prophet

(peace and blessings of Allaah be upon him) entered Makkah on the day
of the Conquest, and there were three hundred and sixty idols around
the Ka’bah. He started hitting them with a stick that he had in his
hand, saying, ‘Truth has come and falsehood has vanished. Truth has
come and faslehood can neither create nor resurrect anything.” (Narrated
by al-Bukhaari). 

Another example was narrated by al-Bukhaari in his Saheeh,
in the hadeeth of Jareer ibn ‘Abd-Allaah al-Bajali (may Allaah be pleased
with him) who said, “The Messenger of Allaah

(peace and blessings of Allaah be upon him) said to me, ‘Won’t you relieve
me from Dhul-Khalasah?’ I replied, ‘Yes, (I will relieveyou).’ So I went along with one hundred and fiftycavalry from the tribe of Ahmas who were skillful in ridinghorses. I used not to sit firmly on a horse, so I informedthe Prophet

(peace and blessings of Allaah be upon him) of that, and he hit my chest
with hishand till I saw the marks of his hand
on my chest andhe said, ‘O Allah! Make him firm
and one who guidesothers and is guided (on the
right path).’ Since then Ihave never fallen
from a horse. Dhul-l-Khalasah was ahouse in
Yemen belonging to the tribe of Jath’am andBajeelah, and in it there were idols which were worshipped, and
it was called al-ka’bah.” Jareer wentthere,
burnt it with fire and destroyed it.  

When Jareer came to Yemen, there was a man who used to
tell fortunes and give good omens by casting arrows of divination.
Someone said to him, “The
messenger of the Messenger of Allaah

(peace and blessings of Allaah be upon him) is here, is present here
and if he should get hold of you, hewill chop
off your head.” One day while the man was usingthem (i.e. arrows of divination), Jareer stopped there andsaid to him, “Break them (i.e. the arrows) and testifythat None has the right to be worshipped except Allaah, or else
I will chop off your head.” So the man brokethose
arrows and testified that none has the right to be
worshipped except Allah. Then Jareer sent a man calledAbu Artaa’ah from the tribe of Ahmas to the Prophet

(peace and blessings of Allaah be upon him) toconvey
the good news (that Dhul-Khalasah had been destroyed). So when the messenger reached the Prophet

(peace and blessings of Allaah be upon him), he said, “O
Messenger of Allaah! By Him Who sent you with the Truth, I did not come
until I left it like a scabby camel.” Thenthe
Prophet

(peace and blessings of Allaah be upon him)  said, “May
Allaah bless the horses of Ahmas and their men,”five
times.

The relevant points in this hadeeth are two: what he
did to Dhul-Khalasah, and how he dealt with the one who used arrows
for fortune-telling etc. 

And it says in al-Fath: “This hadeeth indicates
that it is prescribed in Islam to remove things by which people may
be tempted, be they buildings or other things, even if it is a person,
an animal or an inanimate object.” (8/73) 

Another example is when Khaalid ibn al-Waleed (may Allaah
be pleased with him) was sent to al-‘Uzza and he cut down the three
gum-acacia trees and destroyed the house. When he told him what he had
done, the Prophet

(peace and blessings of Allaah be upon him) told him that he had not
done anything. He told him to go back and find that naked woman with
dishevelled hair who was pouring dust on her head, and so he went back
and killed her with a sword… When he came back to the Prophet

(peace and blessings of Allaah be upon him) and told him, the Messenger
of Allaah

(peace and blessings of Allaah be upon him) said, “That was al-‘Uzza”
(Zaad al-Ma’aad, 3/414). 

It was narrated from one of the salaf that he passed
by two boys who were playing in a hole in which there were pebbles with
which they were playing. He blocked it up and forbade them to go there.
Tafseer al-Qurtubi, 8/340 

But if the one who is enjoing good and forbidding evil
is unable to remove the evil completely, then he should strive to reduce
it as much as possible. 

Ibn al-Qayyim (may Allaah have mercy on him) said, when
mentioning some of the lessons learned from the battle of Tabook, “We
also learn that places of sin in which Allaah and His Messenger are
disobeyed are to be burned and destroyed, as the Messenger of Allaah

(peace and blessings of Allaah be upon him) burned the masjid al-diraar
(a mosque built by way of harming and diselief, cf. al-Tawbah 9:107)
and commanded that it should be destroyed. This was a mosque in which
prayers were offered and the name of Allaah was mentioned, but it had
been built to cause harm and divide the believers, and as a refuge for
the hypocrites. In the case of places of this type, the ruler 
has to put a stop to it, either by destroying it and burning it, or
by changing its appearance and using it for a different purpose. If
this was the case concerning a mosque built for harming and disbelief,
then places of shirk whose cutodians promote taking those inside them
as rivals to Allaah are even more deserving of being destroyed. The
same applies to places of sin and immorality, such as bars and places
of evil. ‘Umar ibn al-Khattaab burned an entire village in which wine
was sold, and he burned the shop of Ruwayshid al-Thaqafi and called
him Fuwaysiq. [Ruwayshid comes from a word meaning “guided” and Fuwaysiq
comes from a word meaning “immoral.” – Translator].  And he burned
the fortress of Sa’d in which he was hiding away from people. The Messenger
of Allaah

(peace and blessings of Allaah be upon him) wanted to burn down the
houses of those who did not attend prayers in congregation or Jumu’ah
prayers; the only thing that kept him from doing that was the woman
and children who were not obliged to attend these prayers, as he told
us. (Zaad al-Ma’aad, 3/571-572)