Not saying I agree with being negative rom the off, preemptive negativity isn't my thing but I also believe he is entitled to moan.
Used to have one near me in the family stand, big ginger bloke ALWAYS shouting at Manga, he'd have a good game and could play blinder for 93.5 minutes and do something ng in the last second and this big ginger ****er would moan, he'd get one in every week. I just ignored him. There was a bloke shouting at Bowler yesterday, highlight of the first 10 minutes was when he shouted something about his hairband..plenty of people were talking about how shit he was but this bloke decided to shouty it through the game, you get them.
Maybe tell them next time, unless they post on here they won't be aware of how they've upset loads of people