Oh, I think he can express anything he wants. But, when you bring an opinion into a public forum, people are going to react, and although there are definitely limits, I think anyone can call bullshit on something when they think it's bullshit.
I don't know Perry from a hole in the ground, and he's probably a nice enough fellow, but the stuff he puts faith doesn't convince me of anything much.
It's stuff I considered and discarded long ago as not only unsupportable by known facts, but pretty emotionally unsatifying too. The fundamentalist/Evangelical version of God leaves me quite unmoved, I'm afraid.