“He’s only making himself look bad trashing her like this,” a source tells HollywoodLife.com exclusively.

“She thinks he’s mad because she stopped returning his calls and moved on to someone younger and hotter,” the insider also shares with us (obviously referring to the extremely yummy Tristan Thompson, 25). “James is a bitter ex-boyfriend, and he’s in her past.”

As for what Khloe will do if James ever wants to try to win her back? “She’s with Tristan now and he’s an upgrade in every way,” the source declares.