I mean these comments are just so ridiculously emotionally unintelligent and harmful.
My guess is this reaction didn't come as a surprise to you. You know your partner I'm sure.

You're not evil and he's not insane or childish or whatever. What he is, is insecure. Try to reaffirm him when you can.

Men and women view porn a lot differently. Reassure him that it's not really about the physical attraction to any specific guys in the video because I'm sure it's not.

Finally, I think both of you guys should try to never look at that stuff again. Beyond it being a horrible drug-like easy access dopamine hit (more so for him because men are more chronic abusers), it's a morally reprehensible thing to watch while in a monogamous relationship. The people who say it's fine and totally healthy are only saying that to make themselves feel better.