Calling someone a "WuMao" is saying that the person is PAID to support the Chinese government, regardless of their actual opinions, and the target of support isn't in the term itself. Calling someone a "trump supporter" doesn't include the part about getting paid.

There seems to be a negative connotation with getting paid to support something, that you're just in it for the money and don't actually mean it.

Of course there are many nuances to the whole issue of labels which I don't have the knowledge or time to go into.