I think you answered your own question. He upped and left and sounds like an ass. Understandable to be a bit miffed at the thought of unknowingly raising a serial killer's child for many years, but he left Tara behind too. I'm guessing he'd be pretty resentful of Sam for being the cause of everything that's happened in 5 and 6.I don't see why he would detest Sam? Like, it's not her fault his wife had cheated and lied for 13 years. And he's kinda trash for leaving them high and dry like that after finding out the truth. Like, they're still his daughters.
But I think we can assume that both Carpenter parents are grade-A dickheads. Imagine your kids going through all that, and you not even checking in on them.