In a nutshell, I will consider conservatism to have become a sane and legitimate movement when it renounces the following:
1) endorsement of creationism
2) endorsement of global-warming denialism
3) intent to make abortion illegal
4) opposition to gay equality, including civil marriage
The first two are rooted in reality-denial and contempt for science; the last two in cruelty, bigotry and sexual puritanism. All of them are directly or indirectly rooted in religious fundamentalism. In brief, a sane conservatism means a secular conservatism.
There are few conservatives who renounce all four of the above, but there are a fair number who renounce two or three of them. Those are the people I'm pinning my hopes on.
Debates about the proper size and role of government, about the best strategies for national defense, about how we can deal most effectively with global warming, etc. are debates that we need to have. Conservative viewpoints on those issues are not delusional or hateful, merely different. We need a political force to represent them. We don't need a political force representing reality-denial, hatred, and religious fanaticism. Right now the latter element has the upper hand within the right. That's what must change.