[ColinWright]

> Who is to say that a post should or shouldn't be on the site

The mods, and the community.

> Flagging should be used for illegal, dangerous, and malicious content like gore, doxxing, viruses, etc.

Flagging is for when you think it doesn't belong. I agree with you that simply disagreeing with a post or comment isn't a reason to flag it, but when you think something is inappropriate for the site then you have a reason to flag it. Otherwise it becomes a complete free-for-all, with no focus, and experience tells us that that's a bad thing.

And you can't downvote a submission.