I concur, it's not a matter of some of these people being dumb, it's about them being too radical. If the Republicans expect to remain a viable party, they cannot continue to purge moderates.
Really? You mean the people who ruined the GOP's image in the early Bush years with their prolific spending and lack of any resemblance of fiscal restraint? There's a reason that Republicans have a far less favorable opinion of their own party than Democrats do. People respond well to politicians making responsible choices--take a look at McDonnell and Christie in Virginia and New Jersey to see what nominating stalwart Conservatives did to the GOP. These people are making the spending cuts that moderates considered to be "too extreme" or "too controversial" and are highly popular in their states for doing so.
So if you think the GOP is going to die by daring embracing Conservatism again, I have to one thing to say. People support elected officials to make actual policy changes--not to get re-elected. If the getting tangible fiscal restraint means no return to the "Permanent Republican Majority" of the Bush Years, that's fine by me.