Why people are so mean

I work for Walmart as customer service representative USA account and actually like 80% of people calling are pretty nice and sweet they just need help doing something and I actually like helping them but the other 20% are so rude and mean they really pissing me off like I get it that the company fucked you over but wtf are you being rude and mean to someone on the phone that's not responsible for your issue and just trying to help you they're sick people like someone yesterday called and he is literally drunk he is mad because he has an issue he swears and talking so loud like why man he is mad because of 12 bucks or something another call it was a nice lady literally she ordered a tv for over a thousand bucks and it didn't got to here but she knows that it's not my fault she was so nice and sweet although she is missing a thousand bucks tv the other dude is yapping about 12 bucks what an asshole but fortunately most of them are really sweet and I love talking to them and helping them