People do not need to be nice to you. Especially if you’re being rude, trying to get something out them, or yelling at them for something. It becomes the cowards response to go “I thought you where nice.” Because News Flash, people tend to be nice to people they like and who don’t treat them like workhorses who exist only to amuse you. 

It becomes the “nice” person’s problem to be ‘nice’ all the time, but others? Nah. They can be as big a bunch of jerks they want. “I thought you where nice” is a phrase I’ve seen a lot of assholes use to defend themselves when the ‘nice’ people get sick of their shit. 

Nobody is nice forever. There is only so much a person can take.