Is it permissible to invite non-Muslim political leaders to address Muslims in the Musaajid?
It is not permissible to allow even Muslim politicians to address the jamaat in a Musjid. The Musjid is not established for the stupidities, baatil and kufr which the politicians pedal. Allowing a non-Muslim into the Musjid is a sin of an aggravated nature because a non-Muslim is always in the state of janaabat. He is ritually impure, hence admission to the Musjid is haraam. Even ritually impure Muslims may not enter the Musjid. If a non-Muslim wishes to visit a Musjid to see how Muslims worship, he may enter if he agrees to take a full bath (ghusl) as Muslims are required to do when purifying themselves from janaabat.
Reference : TheMajlis.net