Matt Damon has not been impressed by the manner in which Ben Affleck has handled his divorce – and an insider exclusively tells In Touch that he’s laying into his old friend with both barrels and sticking up for Jennifer Lopez in a big way.

“J. Lo has been confiding a lot in Matt, not just in Toronto but during recent weeks as well,” the source reveals. “She’s found him to be a calming influence and is hopeful their friendship will last beyond the marriage, plus she’d like to work with him down the line, too.”

The insider adds, “It’s been very difficult for Matt to sit by and condone or even forgive Ben’s behavior, which he finds cruel and totally unwarranted.”

“He’s not trying to butt in for the sake of it and can see very well that life with J. Lo was likely a challenge, but not to a point where she deserved to be humiliated and degraded,” the source continues. “Matt’s big on manners. His wife, Luciana [Barroso], also agrees that Ben’s handled this situation with a serious lack of empathy or class. And they’ve not been shy letting him know that.”

Jennifer, 55, filed for divorce from Ben, 52, after two years of marriage in August. Just weeks after the filing, she and Matt attended the premiere of their new movie, Unstoppable, at the Toronto International Film Festival on September 6. Ben – who produced the film alongside Matt, 53 – was noticeably absent from the event, though the Martian actor and Jennifer were spotted having a personal conversation.

At the time, a source told People that “Jen and Matt began talking and had a long, deep conversation.” The insider continued, “The two friends laughed and spoke more seriously, and for several minutes, they clasped hands as they spoke.”

An additional source previously told In Touch that Matt felt “pretty bad” for Jennifer in light of the split. “He’s been liaising with her on the roll out of the movie so he’s on calls with her all the time and she has opened up to him about how much she’s hurting,” the insider shared. “He’s been trying to reason with Ben to be a little bit more compassionate to the fact that she’s humiliated right now.”

While the source said that Matt’s “loyalty is always going to be to Ben,” the insider acknowledged that “he’s known the guy for long enough to know he has his demons and is by no means perfect.”

Matt Damon Finds Ben Affleck’s Behavior ‘Cruel’ Amid Jennifer Lopez Divorce: ‘Very Difficult’
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He can’t help but feel a lot of sympathy for J. Lo,” the source said about the Jason Bourne star. “He’s trying to play Switzerland and smooth things over on both sides, but Ben is not taking it well at all. To even suggest that he was somehow at fault really rubs him the wrong way. He says if Matt, or anyone, were in his shoes they would have run from that marriage ten times faster.”

After noting that Matt was in a “tough spot” because he wants to support Ben, “he’s also got to maintain this relationship with J. Lo and when he hears her side of things he just feels awful for her.”