SXB - Contrary to what some customer facing staff on this board may say, venting your anger at a service provider for screwing up your travel is perfectly acceptable as long as it doesn't overstep the bounds of civility. Personal insults, swearing, threatening behaviour are not acceptable but venting your anger certainly is.
What you say there is half the problem. If people vent their anger for a screwed up travel plans that is fine, if a bit annoying. The problem is that more and more these days it is becoming personal and threatening.