You are right about it because many content creators from YouTube use TikTok too now. They don’t even film separate videos for TikTok users. However, they simply post their old YouTube videos and still get attention, followers, and likes.
It might help to hire an SMM specialist. Hence, they moderate the comment session and ban all the offensive (not just negative) comments. If you can figure out the root of those messages, you can take more effective action against them.