Im sorry but I had to smile when I read this. In a perfect mens world, his woman would not even look at other men, no matter if they expose sixpacks or anything. And similiar in a perfect womens world, their man would not even look at any other woman in a sexual manner.

It 'just' liking pictures on instagram. I lived before social media was a thing, and I realize how stupid it is to have fights and arguments about instagram. The most stupid example is when because of technical issues, someone whos as "online" and doesnt respond, and people end up in arguments of "why didnt you respond to me, i saw you online". So I always want to think that, for everyones own saneness, to now give too much weight to any of these online things.

Your issue comes down to boundries. You dont like him liking naked women on IG. Its a valid point. Asking him to stop might be valid, but is it really a big issue? If thats one of your boundries, then he should respect it. But what made me smile is that he put up the boundry of you liking pictures of his friends.

If you guys have a background of someone cheating, then thats a whole different topic. If it triggers you when he does it, then its a very valid point to ask him to stop (or vice versa).