You're definitely overthinking this. I'm not trying to make excuses for what your brother said and think it's a terrible thing to say, but you need to look at the big picture here. I think you're the one being petty. You disowned your brother, who has a drug problem and was probably high when he did it, over one racist comment on social media. Not to mention, there are plenty of keyboard warriors out there who will post things they would never dare say in person. Doesn't that sound a little ridiculous to you when you look at it that way?

I feel guilty publicly posting anything to remember him because of what he did to my African American classmate.

What did he do to your classmate? A person whom your classmate has never even met made one racist comment about him on social media. Is it right? No. Did it hurt his feelings? Possibly. Is it the end of the world? Far from it. If a stranger made a rude comment about me on Facebook, I'd brush it off and go on with my life. I suspect most adults would do the same. Your classmate is obviously a smart man and has better things to worry about if he's in medical school. I can't imagine that a year later he's still dwelling on a stranger's Facebook comment.

I think what you're really upset about here is that your brother embarrassed you when he made that comment and that you've spent the past year having no relationship with him because of it. You already explained the situation and his drug problems to your circle of friends. At the end of the day, you're not responsible for what your adult brother says or does. You made it clear you didn't endorse his speech. That's really all you can do. If your friends would expect you not to mourn the death of your own brother a year later over something like this, then they aren't very good friends. That said, I doubt that's what is really going on here. In all likelihood, they probably either didn't even see the post about his passing or just didn't know what to say. A lot people feel awkward commenting on the death of someone they didn't know, myself included. You need to let this go. You're stressing yourself out over something very trivial.

It's just a thought, but I think you would possibly feel better if you did something to help other families going through similar situations, like volunteering at a rehab center or some other charity relating to substance abuse.