Shaykh Ubayd Al-Jaabiree said, “What is well known regarding the situation of the innovators is (their) playing, plotting and trickery; and as such when a man from Ahlu Sunnah comes to them they use him as a means to get strength and support and as a means to delude the weak and unintelligent ones- those who do not have fiqh (proper understanding of the religion) from Ahlu Sunnah; and from this what I see (regarding this matter) is that you do not go to their masajid or their gatherings, so long as they have control over the place, and where the authority is theirs; so do not go to them.
But if it is a place where the people of the masjid are the general common folk and those who prevail over the masjid are the general common folk and these innovators don’t really have any say or control there, then go to them. Clarify the sunnah in that masjid and with Allaah is the guidance…” Ref: IlmOnline
Shaykh al Albaani said, “…The (Salafi) caller should stipulate conditions on them (the innovators who are the administration for that masjid of bidah) and they must not stipulate conditions on him. Also the caller does not surprise them but he tells them what he will talk about.”(1) Ref: salafi talk.net
1) At the end of the answer regarding this question a student summarises the shaykhs answer in the presence of Shaykh Albaani. He says, “That if the (Salafi) student of knowledge goes (to give a talk in a masjid upon bidah) he must clarify the (Salafi) manhaj and mention the differences between us and them (the attendees and administration of that masjid).” Shaykh Albaani agreed with this summeration of his original answer.
Posted by Abdul Kareem Ibn Ozzie