Boyfriend immature? Racist and sexist jokes..?

Thoughts needed. I saw on my boyfriends phone (was sortas snooping but not really, it was open and beside me) messages he was sending to people at school. I know he has an "off" sense of humour and have come to (mostly) accept it. But I guess he tones it down around me and my fam/friends. The jokes he was texting to his school mates were verrrrry innappropriate/offensive stuff, like racism, wife beating, etc. Things I would never say even jokingly. I am a social worker for one thing, and I have done quite a bit or education on how these things, even jokingly, can impact people, and it just goes against my professional and personal value system. I think "jokes" can often hurt the most, and can normalize stereotypes and behaviours that I find unacceptable like violence, sexism, and racism.

He is in trade school for two months, so these are all new people that he doesn't really know and won't likely know for very long, but he met some in his first few days and is carpooling now with a few of them. He told me at the beginning he thought that many of the guys were pretty bigoted, and I expressed my opinion of that (not positive) and said at least he didnt need to really get to know these people or hang out with them, just make pleasant enough to get through the two months. So it surprised me to read these texts. I am assuming its because he wants to "fit in" with these guys and that actually makes me more upset because 1) He gave me the impression he didnt really like these guys and their attitudes and therefore wouldnt feel the need to befriend them 2) Even if he did get to know them I thought he'd be more mature than to stoop to their level.

I let my boyfriend know I saw the texts and was surprised. He acted mildly embarassed and then changed the topic and I haven't approached it since, but it has been bothering me (obviously). I think it shows great immaturity, whether or not the jokes ae because he's trying to fit-in or bond with these guys (which I dont really understand because as I said he will only see these people for two months anyways), or because he actually thinks they are funny or believes in the premises the jokes suggest (which I don't believe he does as normally he is not like that, but then again, my boyfriend keeps a lot to himself and is hard to read, even after the many years we have been together). Lastly, he is 32! The majority of guys in his class are early-twenties. They call him "pops". In my mind, an emotionally mature 32 year old should be able to laugh these things off and be pleasant to his classmates/carpoolers without feelin the need to encourage what even he has admitted he feels is inappropriate behaviour.

On the other hand, I feel guilty that this is bothering me so much as I know there are much worse issues to have and other than my own discomfort/sadness about it it's not effecting other areas of the relationship (other than my trust and opinion of him I guess). Like I said, he doesnt make these jokes/comments to or in front of me.

Sorry this went on so long but Id appreciate any feedback, thoughts, etc. Am I over-reacting? Do you think I can come to accept this behaviour even though it clashes with my values and beliefs? Should I just accept this as a "guy thing" or "tradesperson thing" that has become a normalized part of the socialization aspect of work/school?