"If he invited me to a public hanging, I’d be on the front row."Given Mississippi's long and brutal history of lynchings, it was a rather ill-advised comment.
I admit I've never heard this expression before. But from context, it sounds like the idea behind it is something like "I like this guy so much, if he asked me to do something facially unpleasant, I'd throw myself into it in the most enthusiastic manner possible."
And as an expression of GOP racism, it's hard to think of a more apt metaphor.