I know what you mean OP. I only know three, maybe four men out of all of the men I know who I would consider "non-sexist". And even they slip into saying or doing things that make me want to point out "Your privilege is showing" every now and again. (Plus, I met two of the "definite" ones on the internet, so it's not exactly putting the votes in for randomly running across non-sexist men.)
For example, DP made an offhand comment to me the other day that I would get on with some women that he met because "They have a really feminist household! Everything gets run by them, it might be the mens' names on everything but nothing gets done until it's been run by the women, they're in charge and make all the decisions."
I mentioned this to my friend and she looked equally unimpressed and immediately said "God, what a nightmare. That sounds exhausting!" I think sometimes women just get it in a way that men have to consciously learn and look for and think about deeply, not fleetingly, to understand. We understand sexism inherently by living it. Men are in the position of privilege when compared to women, and part of having privilege is not being aware that you are privileged even if you're sort of vaguely aware that the "other" group are disadvantaged.
However, DP grew up in a very female-heavy household and was always brought up not to even consider that women might not be able to do the things men do. So often when he is saying/doing stuff which is privileged it's because he literally doesn't know that is particularly more difficult for women or frowned upon for women or whatever because in his experience, women do exactly the same things as men, and nobody questions it for a second. Plus, he treats men and women the same (in general and) in terms of hiring employees etc so he was baffled when I was stressing about certain things in a job application because of being a woman etc. Little things like that, and it does bother me, but it only comes out occasionally. Our relationship works because we feel on a level with each other and we have shared goals and values. I do not have to micromanage the housework for example - he's more likely to micromanage me.
So although he's not a perfect feminist all the time, because his heart is in the right place and his intentions are genuine, it's not an issue for me that he doesn't understand what it is like to be a woman. Of course he doesn't, because he isn't one.
I love this article about "co piloting" in a relationship - it sums it up for me. If we have shared values it perhaps doesn't matter so much how we express those values. I know that despite his sometimes infuriating or clumsy way of expressing things, he believes that men and women are of equal value and standing, it's just that he calls that normal and I call it feminism. He thinks that the majority of people in the world already think this and it's just a few idiots who don't, I can see there is still a really fucking long way to go, but I admire his enthusiasm.