Fh’s Bestman not coming to Bachelor party.

So my fiancé’s BM is the only person who said no to not coming on the combined bachelor/bachelorette trip we have planned. We made the trip as cheap as we possibly can and asked everyone their budgets ahead of time and when it went a little over me and my FH chose to pay the difference. I know it’s not because he can’t afford it because he’s been telling FH about all the money he’s making now that he has a new job and has nothing to spend it on. We invited his BM over for dinner and I cooked his favorite thing and he never said thank you or offered to help clean and then backed out on our plans for later that night because he apparently planned to go out the next night with other friends. He planned all of that after committing to our plans. FH and him have been friends since they were 12 and lived together for the past year. It amazes me that he can just act like this whole thing is unimportant. I want to have a talk with him about it because I know it hurts my FHs feelings but he’s a guy so he would never say it. How do I say “hey stop being a bumhole to your best friend and help him celebrate.” In a nice way😶