You seem to misunderstand that this is the purpose of censorship by China. It makes political opposition "taboo". To criticize the leader is to seem "dirty", "sus", and "rude".

The rest is done by the desire for social acceptance.

Midjourney is playing directly into China's censorship.

If homosexuality makes people uncomfortable in the Middle East, should Midjourney ban non-sexual depictions of same-sex couples?