The word "liberalism" is ambiguous. If it is used in the sense of lowering moral standards, obviously everybody is morally obligated to counteract. On the other hand, liberating ethics from the grip of religious (or other) elites can and should result in more adequate moral standards, which are easier to implement and thus result in higher levels of morality.

Religious leaders should insist on the highest realistic standards of morality, but leave it to the experts to find out what these are. This must not be confused with genuinely religious practices such as food taboos - each religious community must find out which of these are really essential. Catholic doctrine seem to have become fairly "liberal" in that respect quite a while ago.