I hope I don’t offend by bringing this back to age, but I do think it is a factor here. A lot of younger guys are all taking PREP and Truvada and attitudes amongst younger people, and certain circles of gay men at any age (probably more so in cities), are very different about condomless sex now than they used to be even a few years ago. As in many guys are having sex without condoms in all types of situations.
I actually had something similar to this happen to me last year. But I asked the masseur to stop (not blaming you or anything for being in shock and unable to say something) after a few seconds after he entered me, and I asked him if he has condoms. And I told him I’m not on PREP and he was pretty surprised. I guess if I wasn’t as aware about what other guys are doing, I would be shocked that he would have sex with me without a condom, and mentally I would have reacted to the situation differently, but honestly I wasn’t upset and I’m sorry the OP felt different experiencing something similar.
So I’m not sure what to make of how people are labeling the OPs situation. My masseur didn’t ask me if he could fuck me, but I could tell that’s where things were headed (also grazing his dick on my ass). And again because I knew attitudes about condomless sex have changed, I wasn’t as shocked by what was happening. I went to his house knowing any type of sex was a possibility (we didn’t agree to anything ahead of time, I didn’t want to).