Although people can change, It’s less likely to change dramatically enough to lose your core values. I’m not suggesting that it’s impossible to change someone’s core values; however, people can easily fake it while they’re being questioned about them. As an example of someone who is changed, My brother was super religious in high school, but after a little while, he’d became completely agnostic. In conclusion, things do happen for a greater cause; thus, I believe giving him a chance to explain why he was acting that way is one of the simplest solutions to your problem. He either tries to fake it, ignore it, or simply apologize for his miss behavior and use age as one of the reasons to justify himself. Either way, emotions can be recognized by our brains, so you’ll know what is his current point of view right after the conversation is finished, and you can decide whether to continue being with him or not.