What the literal fuck..

Okay so first let me just say that yes, I am white (German- though that shouldn't matter). I'm also a bartender. So it is honestly my job to card you or refuse you service if I feel something fishy is going on. Okay, so here we go. Storytime/rant. Tonight I was at work just minding my own damned business, doing some dishes while my patrons drank and this group of girls come in, They're all clearly of age but I card them all anyways. A few minutes later this older, I'd say early/mid thirties black woman comes in and I tried to card her as well (due to the amount of underage drinking/fake ID's in my area my boss requires us to card EVERYONE especially on Saturday nights) and she starts yelling at me that she's of age, and that her ID is in the car. I can't let her in without an ID. If I do I'll get in trouble, so I tell her she has to go get it or find somewhere else to drink tonight and goes off on me. She literally stood there for almost 15 minutes yelling and screaming at me calling me racist and a slave owner as well as some pretty racist comments towards white people. What the literal fuck though? Like I'm not racist, I was just doing my fucking job... so I'm curious. Do you think it's possible for POC to be racist? Racism is racism, right? No matter who it's against.