Why do some white people get angry when I ask them to recall a time they were discrimiated against?

I asked a question like this earlier, I got a lot of thumbs down and some angry answers, but none of them had an experience with discrimination involved. Some said "if black people don't like white people because their white, thats discrimiation" That is not discrimination. That's bigotry. Kind of different, since these people have no power to deny them anything to white people except their friendships. Should I conclude that it's because it never happens?