I don't trust all men on one basis: male socialization, which applies to all of them. To differing degrees and in different ways, sure, but still. Male socialization teaches them to look to women as inferior, as servile, as the ones to blame for their own actions toward them, as fleshy sex toys for their benefit, to be predators of women, to get the most they can for themselves short of it being unacceptable, to be blind to suffering in favor of "rational" principle, to be complicit and overlook the brutality and arrogance of their own group.

Then, it even goes as far as to have them suppress and shame their own emotions, so that they will remain effective as oppressors who will refrain from turning against their own group, who tends to even be shitty to them. No, he's not really a nice guy if he watches porn, and absolutely so if he is protective of his porn habits. If your boyfriend only considers the problem of it to be how its technically cheating to him, he either hasn't realized or doesn't care about the real problem of it.

I can only come to start trying to trust men who hate men themselves, which of course comes down to what the cult of masculinity demanded he himself become. However, even they have to be questioned on whether they are actual traitors to men or if they are simply that cunning to win your trust to then betray you personally. After all, the abusers who get the farthest are those who did the most in their power to avoid being recognized as one.