They tried to do the same with rock way back when.

Germany banned Jazz and other "black music".

Because during their respective popularities in their countries, they became a source of rebellion of thought.

Whatever you think of rap is irrelevant. A government is attempting to exert control on artistic expression because it doesn't like criticism or diversity of ideas among its populace. An attempt to control thought and new ideas,

Every generation has had a musical boogeyman that was thought evil or wrong. Even as far back as classical music genres. With many resistance especially comin from the Church. The attempt to stifle new music is the fear of change. A weapon of oppression and bigotries.

In antiquity, the boogeymen were pagans, impiety and the devil. In the last century anti-conformity and blacks.

In Russia, western ideas, anti-governmental criticism, and the old sex, drugs, and rock and roll rap.

US tried censorship of rap in the 80s and 90s. It became even more popular. Many themes turned instead to anti-governmental protest and intentionally objectionable subjects and language. Using the very language the government attempted to curb to an even greater degree.

People tend to rebel against the stifling boot on their artistic necks.