Is it permissible to pray behind a mosque imam who supports Bashar al-Assad?

If supporting the Nusayris is based on the belief that they are disbelievers, then prayer behind the supporter is not valid, because prayer behind an innovator whose innovation is considered disbelief is not valid. Sheikh al-Islam Ibn Taymiyyah clarified that the Nusayris and Qaramita are greater disbelievers than the Jews, Christians, and many polytheists.

However, if the supporter does not share their disbelieving beliefs, but rather supported them due to a misconception, then he is not judged to be a disbeliever. Nevertheless, his support for what the Nusayris do to Muslims makes him a transgressor (fasiq). Prayer behind a transgressor is valid, though disliked, according to the majority of jurists.