The head of the Islamic centre in their city is married to a Christian woman; has he done something for which he deserves to be dismissed from his post?

Marriage of a Muslim man to a woman from the People of the
Book — a Jewish or Christian woman — is permissible in the sharee’ah of
Allaah, because Allaah, may He be glorified and exalted, says
(interpretation of the meaning):

“Made lawful to you
this day are At‑Tayyibaat [all kinds of Halaal (lawful) foods, which Allaah
has made lawful (meat of slaughtered eatable animals, milk products, fats,
vegetables and fruits)]. The food (slaughtered cattle, eatable animals) of
the people of the Scripture (Jews and Christians) is lawful to you and yours
is lawful to them. (Lawful to you in marriage) are chaste women from the
believers and chaste women from those who were given the Scripture (Jews and
Christians) before your time when you have given their due Mahr
(bridal-money given by the husband to his wife at the time of marriage),
desiring chastity (i.e. taking them in legal wedlock) not committing illegal
sexual intercourse, nor taking them as girlfriends. And whosoever
disbelieves in Faith, [i.e. in the Oneness of Allaah and in all the other
Articles of Faith i.e. His (Allaah’s) Angels, His Holy Books, His
Messengers, the Day of Resurrection and Al‑Qadar (Divine Preordainments)],
then fruitless is his work; and in the Hereafter he will be among the losers”

[al-Maa’idah 5:5]. 

The woman of the People of the Book whom it is permissible to
marry is the one who is chaste. 

See the answer to question number
2527. 

Secondly: 

The Prophet (blessings and peace of Allaah be upon him)
commanded men to choose as wives those who are religiously committed and of
good character. The Prophet (blessings and peace of Allaah be upon him)
said: “Choose the one who is religiously-committed, may your hands be rubbed
with dust (i.e., may you prosper).” Narrated by al-Bukhaari (5090) and
Muslim (1466). Hence many of these scholars are of the view that it is
makrooh for a Muslim to marry a woman of the People of the Book. They have
other reasons for regarding this as makrooh, including the following: 

1.Their fear of marrying one who
is not chaste

It was narrated that Shaqeeq ibn Salamah said: Hudhayfah
married a Jewish woman, and ‘Umar wrote to him saying: Let her go. He wrote
to him saying: Are you saying that she is haraam so that I should let her
go? He said: I am not claiming that it is haraam; rather I am worried lest
you marry the immoral ones among them. Narrated by Ibn Jareer al-Tabari in
his Tafseer, 4/366; classed as saheeh by al-Haafiz Ibn Katheer in his
Tafseer, 1/583 

2.Their fear that the Muslims
will begin to marry women of the People of the Book and the Muslim women
will be left without husbands

It was narrated from ‘Aamir ibn ‘Abd-Allaah ibn Nastaas that
Talhah ibn ‘Ubayd-Allaah married the daughter of the Jewish leader and he
said: ‘Umar insisted that he should divorce her. This was narrated by ‘Abd
al-Razzaaq in al-Musannaf, 6/79. 

Ibn Jareer al-Tabari (may Allaah have mercy on him) said,
commenting on what ‘Umar said to Hudhayfah and Talhah: 

Rather ‘Umar objected to Talhah and Hudhayfah (may Allaah
have mercy on them) marrying the Jewish and Christian women lest the people
follow their example in that, and lose interest in the Muslim women, or for
other similar reasons, so he commanded them to let them go. End quote. 

Tafseer al-Tabari, 4/366 

3.Many negative consequences that
may result from such marriages, such as disputes and arguments and dangers
posed to the religious commitment and beliefs of the children

We have mentioned the negative consequences of marriage to
women of the People of the Book in the answer to question number
20227; please read this as it
is important. 

Thirdly: 

The scholars (may Allaah have mercy on them) mentioned a
principle, namely that that which is makrooh is permissible if the Muslim
needs it. 

See this principle and others in Sharh Manzoomat Usool
al-Fiqh wa Qawaa’iduhu  by Shaykh Ibn ‘Uthaymeen, p. 62. 

Based on that, what the head of the Islamic centre has done
is makrooh in principle, but we cannot state that this particular person has
done something that is makrooh in his particular case, because he may have
reasons for that which mean that it cannot be judged to be makrooh. 

If we assume that he has done something makrooh, then he has
not done something haraam; rather he has done something which the Qur’aan
indicates is permissible. 

Such matters do not mean that he is no longer regarded as
being a man of good character, and do not mean that he must be shunned or
dismissed from his post, because he has not done something haraam, and it
does not affect his good character and trustworthiness. Be kind to him and
be united, especially in your country, where you are in great need of being
united and building ties with one another. 

And Allaah knows best.