Don't even.
That guy was...is, a jackass.
He'll just end up stringing you along again, and then end up bedding the next hottest piece of ass he sees behind your back, just like he did before.

If he doesn't expect to get back together with her, I can respect him for at least letting her know karma bit him in the ass.

If he does expect it, then he can expect another sharp set of karma teeth.