They think they do. Who's going to stop them? The Bishops? The Pope? The Laity?
Very good question.
Ultimately, it's up to the laity, with the help of the bishops and the pope.
We haven't been in a situation where ecclesiastical discipline would be effective for a long, long time. So there's not that much that the bishops can do to directly stop it.
The thing they can do is to teach better and act as a moral voice more effectively than what they've done in the past.
In that department, I am encouraged by the bishop's conference appointing Jonathan Reyes (a former Christendom professor) to lead their Justice and Peace department. It was fun watching heads explode on the Catholic left with the news of that appointment.
Seeing Bishop Morlino's defense of Paul Ryan and his proposed budget was also very encouraging.
Seeing Bishop Paprocki's condemnation of the Democrats...and not just for abortion...and his statement that oh, by the way, there are any number of possible solutions to social issues than simply tons of government spending...was also very encouraging.
Seeing the number of bishops who came out against Obamacare, not just because of abortion, but because it violated subsidiarity, was also good (although I admit that I wish there were more).
And so on.
But when it comes down to it, it is all up to the laity. We need more people like Paul Ryan, who actually know social doctrine and endeavor to put it into practice. We need more conservatives to study and understand the social doctrine of the Church and then to get in the face of the lay social worker who runs the parish "social concerns" ministry and who, with respect to the clergy status, are not afraid to confront the parish pastor when he teaches left wing political tripe as Catholic doctrine. We need to infiltrate left wing "religious" meetings and call supposedly "religious" people to task when they misrepresent Church teaching as justification for their actions. And, in the secular sphere, we will need to out Alinsky the Alinskyites.
There is only so much the bishops can do. We laity need to get off our asses and take our Church and our society back from the left.