I thought that it meant "OK, I will accept this self loathing of the line but hey, the line is not bad, why bother?"
Am I right? If I am right, I thought "and" should be "but"
But there I go, adopting Auden’s retroactive self-loathing of the line, and I’m not sure it was such a crime against poetry.
The author employs and to call attention to the fact that he has allowed himself to be seduced by his "self-consciously highbrow culture" into adopting Auden's attitude to the line despite the fact that he doesn't think that attitude is justified.
This is a common way of expressing the notion that one the more culpable for acting against one's true belief or interest:
Dave congratulated him, too, and Dave voted for the other guy.
She's a hell of a salesman. I bought twelve boxes, and I don't even like Girl Scout cookies.
I didn't read the original, but the question to my mind is whether "it" here refers to "the line" or the "retroactive self-loathing". If "it" refers to the self-loathing, then the "and" makes sense: I adopt it, AND it is not a crime. If "it" refers to the line, then it would seem that "but" would be more appropriate.
