De-sinicization is when some people try to remove or get rid of things that are related to China or Chinese culture.
Imagine that you have a favorite toy, and someone comes to your house and tells you that you can't play with it anymore because it comes from a different country. That's what some people are doing with things like Chinese language, art, and traditions. They don't want them to be part of their own country's culture anymore.
It's like a person who doesn't want to eat pizza anymore but wants only to eat hamburgers. They might get rid of all the ingredients and tools they use to make pizza and focus only on hamburgers. That's kind of what de-sinicization is like.
But some people think that it's not fair to get rid of things that are important to other people just because they come from a different country. They believe that everyone should be allowed to enjoy and celebrate different cultures, no matter where they come from.