Yes, I've experienced. If those people are really as bad as you're saying I don't see why you should care about what that guy is saying. What people don't realize is that there is a HUGE difference between talking about someone in any way you'd like and then not faking like you haven't talked shit about them, gossiping, and being a backstabber. BUT it only takes one slip up to make one of those things turn into the other. And there's the biggest difference when you're talking about them but being nice to them in front of their face. Is that what you're doing?
If so...of course people will be even angrier when you're talking about people when it's behind their backs and then when you're in front of them and they've already found out it's not exactly going to be "rainbows, lollipops, and unicorns" with them. They're going to be pissed and you know that. Even if they're horrible I don't see why you should talk about them behind their backs and then being nice to them when you're right in front of them.
And of course people you wouldn't even expect to be mad at you, be mad at you because from talking about people behind their backs it will make them think: "Well..shit..if she/he's talking about them behind their backs..She could be saying something about them". That's simply the kind of crap that comes with talking about people behind their backs to others, expect it. If you don't like someone, don't do that type of stuff..be real with them.
So to sum this all up: If you can't take the heat, stay out of the kitchen and be real with others.
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Happy Halloween!
http://www.youtube.com/watch?v=N9_6IODy0mU