The reason why people rant on internet forums is because they can.
In real life when your boss, the salesperson in the shop, the traffic warden, the person, listening to techno at frightening volume, sitting in front of you on the bus, piss you off......you have to hold your tongue. Because there are consequences to actually saying what you feel in REAL life. On the internet there are none. So when you get narked by the frustrating irritations in your, day to day, life. You can vent by coming onto off topic and letting it rip!