Probably part of the neo-con fascination with who/what people are sleeping with. Snitchens as a new acolyte of the right is looking to proof his cred on all topics, so slagging Clinton for having 'unbecoming' sex is part of that process. Seeing that as far as we can tell Bill isn't gay or bi, he's got to be a hetero degenerate.
My guess too is that it's some lingering English class based resentment about Clinton carrying on with someone 'beneath' his office, or Monica for daring to snog someone 'above' her station.
That, and the nameless dread carried by all Englishmen, manifest as jealousy, that someone is having more sex than they are, they're having more fun while doing it and they're better at it than the English are.
I mean who one earth would find a booze soaked, pedantic wind bag, that reeks of stale tobacco the least bit attractive? Sheesh, Slick Willy's a sex god in comparison.
PC
N P Childs
'I'm Mister Bad Example, the stranger in the dirt, I like to have a good time and I don't care who gets hurt'.
-Mr. Bad Example, W Zevon