Being LGBT isn't the same as being political. It's not a subset of politics. Being accepting of gay people or prejudice against them might align with the two parties in the United States but someone's existence and visibility isn't inherently political. The point is that China (and many others in the world) are taking a stand against LGBT people, not just to preserve their hold on political power.
See TikTok's banning LGBT content and Facebook's banning HIV drug awareness ads.