I suspect that a history of centuries of bloody sectarian conflict between Christians may sometimes make people reluctant to be too outspoken about other branches of Christianity, even where these are seen as deplorable.

I suspect that the same kind of thinking may make many Muslims reluctant to speak out too openly about variants of their religion which are extreme, such as the relatively recent (200 years is recent in this context) development of Wahhabism, which seems to have been been the seed-bed of Jihadism.