I have a lot of respect for MacRanger. Being a guest on his show was quite an experience, and well worth pursuing. That said, with regards to John McCain, he is way off base.
The fact of the matter is that "true" conservatism did not close the sale with the Republican primary electorate in 2008, particularly on what seems to be the litmus test of the past few years, immigration.
And I find it quite telling that people like Mark Levin don't seem to get it, and in fact, seem to be taking issue with people like the folks at Powerline Blog, who point out (correctly) that conservatives are not in a position to make demands on John McCain. Levin's comments are just typical of the poor strategic and tactical sense shown by conservatives in the last few years. And poor strategy, tactics, communications, execution, and interpersonal skills will not be negated by how principled a person is.
Finally, one last note: Losers do not get to dictate terms to the winners. If conservative want McCain to respond to their desires, they have to go to him, and they need to move his way. It would be respectful of the Republican primary electorate. It may even be a matter of their political viability - because it is very likely that the Democratic nomination will end with a significant number of disaffected Democrats, and McCain will more than likely be able to appeal to a lot of them. And if he wins, with folks like Levin loudly campaigning against him because he lacked sufficient purity, he and Republicans will have every reason to ignore conservatives.