Why are they insane? Because you don't understand them?
Just because one may be homosexual, doesn't mean that they can't be Republican. And if they decide to be Republican, it doesn't mean they have to support everything the Republican party is doing. A great example of this is the Log Cabin Republicans. They are loyal Republicans. However, they don't accept the idea of opposing homosexuals. And in fact, many Republicans don't.
The thing is, one can affirm the majority of beliefs of a group, yet still debate other beliefs of that group. We see it all of the time. Maybe these individuals feel that Republicans, on the vast majority of issues, are right. Why shouldn't they be able to be Republican then? And why would that mean they couldn't fight against some of the Republican ideas they don't like?
Republicans are not a completely united front. There are many disagreements. And really, you see this in any belief form. There are many disagreements, and there are internal debates. There is nothing wrong with that though.
So why shouldn't Rush be able to share some of the ideas of Rand, yet reject others and still be a Christian? There is nothing stopping him. And there should be nothing stopping him.