When something is in itself intrinsically wrong (both unethical AND immoral not matter how you look at it), such as slavery or genocide, then all religions and churches, as well as everyone else, have the obligation to speak against and act against it.

The trouble is that there are sometimes different opinions about whether something is "intrinsically wrong" or not.

However the notion that making something illegal should be seen as the only or the best way of stopping it happening just does not stand up to scrutiny. And the judgement on that is about politics, not about morality.