GROAN my DH is a bit like this sometimes.... not always.... He can get a bit moany at cafes and restaurants etc..... Also, I have had occasions when I have just walked away from him, as he sometimes seems to be spoiling for a fight. He is in his mid 50s, and has only been like this really for the last 4 or 5 years.
When he DOES complain, he thinks he comes across as assertive, and clever, and authoritative. But he doesn't, he comes across as obnoxious, and rude, and aggressive. I have been so embarrassed by his behaviour a few times, that I have just walked off.
I have actually gone off on one at him a few times (when we get back to the car,) and told him his behaviour is out of order! When I do this, he doesn't behave like this for a while, but then the rude curmudgeon behaviour creeps back in after a few months.
One chap accidentally caught our trolley about 9 months ago (in Sainsburys,) and DH went mad, and started yelling at him. A member of staff witnessed it, and pulled my DH aside, and told him in no uncertain terms, that he would be banned from the store, if he behaves like that again.
I stormed off back to the car, and said 'if you keep getting into trouble, and even if you get into trouble with the police for being an aggressive arsehole, don't expect ME to be on your side and in your corner, because I WON'T be!' I think it shook him up, and he knew I meant it, because since then, he hasn't behaved like that. Whether he will again time will tell....
I don't know why some people are like this. My BFF's older brother is the same. Moany and shouty and aggressive. WTF? It's like they're angry with life! I literally never, and I mean NEVER behave like this.