It's striking how quick people are to assume that their political opponents (and even their allies!) are just pretending to take morality seriously. There are some cynics out there, but they normally avoid moral argument, rather than engage in it insincerely.
If you think that no one could sincerely hold the moral views they claim to hold, you should try to convince someone to abandon their religion. After a few hours, you'll probably have every right to doubt their rationality. But if you think that "it's all an act," you're just being paranoid.