"They pulled me over for expired tags"

So, you were breaking the law! Enough said!

Perhaps try NOT breaking the law, and I think you will find that these "attitudes" toward you will change just as quickly.

"accuse me of being on drugs, or driving under the influence of alcohol"

I do not believe that they accused you of driving under the influence of alcohol. If they were even mildly suspicious that you were, you would have been subjected to a breathalyzer. Asking if you were drinking, or taking drugs, is not an accusation. It is simply an inquiry.

"I'll use it when it fits the situation"

This is not a racist situation. I see this as just a retaliation from someone who broke the law, and got caught. If you had not broken the law (driving with expired tags), none of this would have happened.