Pretty sure my mom is racist

I have three kids. 2 biological and 1 step son and my mom has always treated him differently. At first I just chalked it up to her being upset me and my ex divorced. But I can't ignore what's right in front of me anymore. I'm pretty sure it's because he's black. My mom doesn't like my husband and doesn't ever want to come meet his family. She doesn't want my biological children around him family either. She asked me if they do drugs. I said no and I didn't understand why she was asking me that. Every time something goes missing she instantly assumes it was my step son. She stereotypes my husband's whole family. She has said things like "You need to watch him. He seems like the type to have sticky fingers." I don't know what she means by that. My step son dresses very professional and doesn't even come across like the type to steal. Ny husband's whole side of the family is so sweet. I had to take a step back and think. I've dated other people before and even some who had kids and she has never treated them this way. Some of you may think I'm overreacting but if you could see how much she stereotypes them it's become blatantly obvious. She is my mother and we have such a close relationship. So I decided to be honest and ask her if it's because they are black. She told me "I work with black people, I'm obvious not racist, however I think you should keep an extra eye on them. Just to be safe." I couldn't believe she said that. I told her "No! Mom that's racist!" She quickly starts defending herself saying there's nothing wrong with wanting to protect me from high risk people. I had to walk away before I said something I would regret. She is still convinced she has done nothing wrong. I love my mom. She was a single mom and all I had, but I will not subject my husband and son to this racism anymore. He's 15 and not stupid. He probably picked up on it way before my dumbass did. Walking away from my mom is hard, but I can't let her toxic view poison my family.