Your experience with rude people shouldn't affect your opinion of all black people. The worst people I deal with are old white folks, but I don't hate all old white folks. Hatred is strong. Really strong. If you hate someone, you might need to take some time for introspection. Sure, people can be rude and annoying and sorry, but fast food customers all tend to be dickish. If you work in an area with a higher concentration of black people and you also work in fast food, statistically speaking you're going to encounter more rude black people than rude people of other melanin amounts. I don't think it has to do with black people as a whole, just about probability of people being dicks. It is something you have to take the time to think critically about. It is a bit racist if you are letting a portion of black people effect your views of the whole race in negative way. Absolutely. Be aware of that. I don't care if this gets downvoted.
I used to work in an uppity, rich area where white people run rampant and the "I'll get you fired" mindset is all too common. PEOPLE can be awful. Does not matter what color they are. But then you start talking about their education because they don't talk like you want them too. That's their culture. When you start talking shit about the way they talk and their education, it gets a little more complicated. That's where your privilege is coming through like crazy.
I'd hate for you to let this time in your life shape your worldview forever. Grow up a little. Experience more than just your fast food bubble. People will a still be dicks, regardless of their skin tone, but hatred seeps in and makes a home. That's something you will have to live with if you let it go too far.