I heard the same thing as mar, that TikTok in China promotes 'the best of the best of youth' and TikTok here is often a cesspool of degenerates, and the difference is in the algos coming out of China.
I don't use it, but I've seen quite a few examples and many of them are definitely people most would consider degenerates.
I'm not on either side of this argument because I don't have enough knowledge or experience with TikTok to have high confidence, but if China was using it as a way of disrupting and degrading our society, that's not free speech, that's infiltration by a foreign power and the differences in the algos should be rather easily provable.