Stroppy, grouchy, cranky, curmudgeonly - all words used to describe me at various times by various people. Difficult, spiky, awkward, nasty piece of work and dangerous have also been applied.
Misanthropy and the refusal to suffer fools gladly have a lot to do with it- that I will freely admit. But I get stroppy when I see people being badly or unfairly treated. I call it out, I get in peoples' faces about it. I get rules changed, managers and supervisors disciplined, offenders fired, people chucked out of shops and pubs and have even been known to engage in fisticuffs (or kick somebody in the wedding tackle) if the situation demanded it.
So if nobody minds - or even if they do - I'll stay stroppy!