I'll agree with Synikul.

Even if I publicly slagged off about a girl, unless I truly, deep-down within myself despised her (which would be highly doubtful as I don't believe in wasting energy on negative emotions), I would still make-out with her if she came onto me and I was drunk, lonely, horny, bored, at a party, etc.

It's what guys do.
You'll find in most tight-knit, semi-alternative, kinda-easy-with-their-morals, teenage groups the girls and guys pass each other around without much thought.
All my friends have either dated, made-out with, or fucked basically everybody else in the friendship group.

Deal with it, man.