I think content providers and platforms should be free to make whatever choice they want regarding content on their platform, provided they don't discriminate illegally (i.e., based on membership in a protected group https://en.wikipedia.org/wiki/Protected_group)

If you fully ramify your position, you're advocating that the government tell me that if I host videos, I can't prevent people from posting videos that I don't like. E.g., if I make a cat video hosting platform, and someone uploads a dog video, I can't stop them.

Again, this is a debate about where to draw the line. It just happens to be the case that there are some people who are fierce advocates for maximizing the amount of gun stuff that is readily available online.