I think the important thing is..
if you have the conviction to put into the story, you will also need the conviction to confront the idea of racism.
There have been many stories that introduce it, but don't have the balls to continue, or deal with it on fears of any retaliation.
For your story, the easiest way to deal with the topic if included into the story, would be to say it, then have the mc stomp it out right there and then like, "Hey im saving your ass." and save the one who'd said it without threats, violence, or the "-so bite your tongue" half of the argument. have the one who said it feel some kind of remorse about saying it, but don't have them apologize just yet. let the action roll out. apologize when things are all in the clear and they're actually all safe; something as easy as "I had time to think about it, i was wrong." Done, ended racism (within the story)! yay!
The hard way would be to let it linger without the apology, or by effectively adding the second half of the argument, "im saving you so shut the hell up!" Neither side winning the argument. Doing this, you've essentially put it in your back pocket to deal with later, having the racism topic hovering over the air throughout the rest of the book until you write another opportunity to discuss the topic, and having to create another conflict with it...
You can always have a middle ground to work with, people write about racism everyday, keeping it hovering around the surface of their books, through visuals, and backgrounds, through npcs, and against one or two of their main group MCs, having it as a constant battle throughout the story. But that's for better writers than myself. I only dabble with the topic through demons vs angels, or monsters vs humans. I don't outright have race wars, or anything remotely near it. I Just wanted to throw my dime into the ring from what I've learned reading books.
