The reason why the one to whom a homosexual act is done is to be executed

Al-Tirmidhi
(1456), Abu Dawood (4462) and Ibn Maajah (2561) narrated that Ibn ‘Abbaas
(may Allaah be pleased with him) said: The Messenger of Allaah (peace
and blessings of Allaah be upon him) said: “Whoever you find doing the
action of the people of Loot, execute the one who does it and the one to
whom it is done.” Classed as saheeh by al-Albaani in Saheeh al-Tirmidhi. 

The Sahaabah
were unanimously agreed on the executing of homosexuals, but they differed
as to how they were to be executed. 

Some of
them, such as Abu Bakr al-Siddeeq and ‘Ali ibn Abi Taalib (may Allaah be
pleased with them) thought that they should be burned to death. Some of
them, such as Ibn ‘Abbaas (may Allaah be pleased with him) thought that they
should be thrown from a tall building followed by stoning. Some of them
thought that they should be stoned to death, which was narrated from both
‘Ali and Ibn ‘Abbaas (may Allaah be pleased with them). 

See:
al-Mughni (9/58). 

The reason
why the one to whom such an act is done should also be executed is because
he is a partner in the sin, because this sin can only be committed if both
parties take part, so it is only just to carry out the punishment on both of
them. Similarly in the case of zina (adultery), the punishment is carried
out on both the man and the woman. Moreover there is nothing good to be
gained from letting the one to whom it has been done remain alive, because
of the great evil that has befallen him and because of the great evil that
may result from his presence. 

It says in
Mataalib Ooli al-Nuha (6/174): Even though adultery and homosexuality
are both immoral deeds and are both evils that go against the wisdom of
Allaah in His creation and His command, in homosexuality there are
innumerable evils and it is better for the one to whom it was done to be
executed than to let him repeat that evil action, because he has been
corrupted in such a way that there is no hope of reform for him, and there
is no goodness left in him, and after that he will not feel shy before
Allaah or before His creation. The sperm of the one who did that will affect
his heart and soul as poison affects the body, and he does not deserve to be
guided to anything good, and every time he tries to do something good,
something will happen to spoil his good deed, as a punishment to him. Hardly
ever do you see one who was like that in his youth but he is the worst he
can be when he grows old. He does not gain any beneficial knowledge or do
any righteous deeds, or repent sincerely, in most cases. Once this is
established, the evil consequences of homosexuality are among the worst of
evil consequences, so its punishment is one of the most severe of
punishments in this world and in the Hereafter. 

The
companions of the Messenger of Allaah (peace and blessings of Allaah be
upon him) agreed unanimously that the homosexual is to be executed, and none
of them differed concerning that. Rather they differed as to the method of
execution. Some people thought that this difference means that they
disagreed about executing him, so they narrated it as a matter concerning
which the Sahaabah differed, but it is a matter concerning which there was
consensus among them, not a matter of difference. End quote. 

The source
for this was Ibn al-Qayyim (may Allaah have mercy on him), who mentioned it
in al-Jawaab al-Kaafi li man sa’ala ‘an al-Dawa’ al-Shaafi. 

But if the
one to whom it was done was forced, then he is not to be punished, because
the Prophet (peace and blessings of Allaah be upon him) said: “Allaah
has forgiven my ummah for mistakes and forgetfulness, and what they are
forced to do.” Narrated by Ibn Maajah (2045); classed as saheeh by
al-Albaani in Saheeh Ibn Maajah. 

See also the
answer to question no. 38622
for more information.

And Allaah knows
best.