Am I Being Too Strict About Gay Friendships and Boundaries?

I have this friend whom I’ve known for a couple of years. We have never had sex or dated because he’s always in a monogamous relationship and has very little time being single in between. Additionally, I have already moved out of the city where we met. We only exchange nude pictures and occasionally sext [at the time when we just met, then after a while I stop doing it because he's in a relationship with someone else.] He’s a great friend, and at this moment, I’m pretty sure I’m not interested in dating him or thinking about him when I jerk off.

We still chat occasionally, but he has this little habit that sometimes annoys me. Whenever his boyfriend is not around, he brings up the fact that he still looks at the nude photos I sent him and jerks off to them. Sometimes, he even shares very specific details, like how his d*** is leaking just from looking at pictures of my chest, legs, and bulge. [These days it's always him telling me he jerks off over my pics, I don't do the same to him at all.] To him, it seems like a generous compliment, but for me, I’m not sure how I should feel about it since he’s in a committed relationship.

I’ve tried to give him subtle hints that I don’t think it’s OK. For example, I told him that I’d be interested in meeting his boyfriend and becoming friends in the future, so maybe we shouldn’t chat this way. I also asked him how he would feel if his boyfriend found out about our conversations and his collection of my nude photos. He said it’s no different from looking at Twitter or OnlyFans to get off while in a relationship—except I’m someone he knows. Now, I’ve started just ignoring those messages and only clicking the like button instead of responding.

Do you think I’m being too strict about gay friendships and that this is completely normal? Because I know if a taken straight guy told his female friend that he jerks off to her nude photos, it wouldn’t be OK. I also have this tendency that once I see someone as a friend, I completely lose sexual interest in them, no matter how much I wanted them before. I don’t want to be too harsh and tell him outright that I’m uncomfortable, risking our friendship, because gay adult friendships are already difficult. I want to keep him as a friend.

Does anyone have any advice on how to navigate this situation? Has anyone experienced something similar? Thanks!