While he was quick to disassociate his personal opinions from those of the National Review, the reaction from the magazine's editors made it clear that his resignation was in order, as he explains in Sorry, Dad, I was fired.
Here are some of my favorite quotes:
I retain the fondest feelings for the magazine that my father founded, but I will admit to a certain sadness that an act of publishing a reasoned argument for the opposition should result in acrimony and disavowal.
I have been effectively fatwahed (is that how you spell it?) by the conservative movement, and the magazine that my father founded must now distance itself from me. But then, conservatives have always had a bit of trouble with the concept of diversity. The GOP likes to say it’s a big-tent. Looks more like a yurt to me.
While I regret this development, I am not in mourning, for I no longer have any clear idea what, exactly, the modern conservative movement stands for. Eight years of “conservative” government has brought us a doubled national debt, ruinous expansion of entitlement programs, bridges to nowhere, poster boy Jack Abramoff and an ill-premised, ill-waged war conducted by politicians of breathtaking arrogance. As a sideshow, it brought us a truly obscene attempt at federal intervention in the Terry Schiavo case.
So, to paraphrase a real conservative, Ronald Reagan: I haven’t left the Republican Party. It left me.
If you care to, read Buckley's endorsement: Sorry, Dad, I'm Voting For Obama.