Is it okay to portray a character to be racist inside a novel that I write? Let's say it's important for the storyline.

Of course it is. Read some of the classics. Notice what resonates in your own soul. The writers probably spoke honestly about something disturbing, without falling back on the political correctness (or what-have-you) of their time and place.

You can’t write powerful stories if you're afraid to explore hard things. 🥲