Church clamp down a two-edged sword

The Catholic church, as has been fairly widely reported (see, e.g., here), has begun to punish MPs who had voted for same-sex marriage and against Catholic doctrine.

Many bloggers have commented on this. Those who supported ssm were appalled; those who were opposed, enthused. My view is that the RCs (and other churches) are free to use the whip on their members if they like. But I think they would be wiser not to. There is a potential back-lash here that I think they should be wary of. It was not long ago that JFK had an uphill argument to make in trying to convince protestant America that although a Catholic he did not take marching orders from the pope. Now, the church seems to be saying that all Catholic politicians should do precisely this. But does this mean that we have to begin scrutinizing Catholic politicians more closely than others in order to find out whether they are going to impose church doctrine concerning abortion, divorce, birth control, etc., on the rest of the country? If that process begins, I can only assume that it will work to the detriment of the Church.