It could be that conservatives generally have less taste for risk, and there's a risk in offending large portions of Catholicism by showing disdain for a representative churchman of that faction. You don't want to fray Peter's net too much; you want to *conserve* it.
With Catholic liberals, maybe there's more faith in faith as opposed to reason, and that necessarily means taking greater chances. If you want change, after all, you have to break a few eggs (or egos).
It could be my bias but it always seems like liberal officeholders treat conservative officeholders worse than vice-versa --Trump being the exception (although Lord knows what he is politically). I think Trump's success is partially a reaction of frustration by the GOP base inasmuch as McCain and Romney were perceived as playing too much by "gentlemen rules". Trump, like Francis, plays for broke.