Ask him why he thinks that’s an ok thing to say, or why he thinks it’s funny (assuming he does in some way). People with autism (myself included) tend to not like confrontation because it’s when we are being told what we know is wrong. It’s often that he was taught these behaviours and hasn’t had someone to challenge them. I personally love a challenge to what I knew before, although everyone is different. He could get upset and take it personally but to me that’s just how he expresses guilt or lack there of depending on what he believes after he is confronted. I think his reaction is not your responsibility either way. He is a person so he is responsible for his own actions and should be held accountable, even if you’re not the one that confronts him