Fully prepared to be told IABU, completely lighthearted as I don't care what happens either way 
DH has a friend in work who separated from his wife about a year ago. He and DH don't socialise outside of work, and DH is always saying about how this guy (let's call him Ben) has been enjoying life since the separation by using OLD apps like Tinder and meeting random women for sex. Each to their own.
DH has arranged an evening at our house for him, his best friend and DS (12) to watch some big football final in a couple of weeks. No idea what, sorry, I don't have an interest in football. DH is providing food in the form of pizza, nachos etc and beer for the adults.
He has told me that he has now invited Ben, so we will need to buy an air bed, as with one mate on the sofa, there will not be room for Ben to sleep and he needs to stay as he wants to drink. All fine by me, I will be in the bedroom watching Netflix working.
He came home for lunch today and reminded me about his plans, but mentioned that Ben will probably have a few drinks and leave after the food and football as he will "want a shag". I said that it seemed a little rude, to come for a sleepover type event, eat the food and drink the beer provided then sod off for a better option. DH says IABU because he is entitled to do what he wants (and I 100% agree with him there, it's Ben's life) but if I was going to a planned sleepover/party type thing at a friend's house, I wouldn't drop everyone part way through for a meaningless hump.
DH said it's a perfectly normal thing for men to do, and that it isn't rude in the slightest. I said that as we are having to purchase an air bed when we are pretty skint at the moment, for someone who may or may not stay, it is a bit rude, and that surely someone can not have sex just for one, planned evening to spend time with friends.
So AIBU? It's rude, right? Or perhaps not and I am wrong. Like I said, whether he leaves or not doesn't bother me, I'm not involved directly anyway, but it just seems a bit...usey.