But just because people disagree about something doesn't mean it's purely subjective. Some things have an objective truth value but people will still disagree on it, because people get things wrong sometimes. Objectively wrong. All the time, in fact.
You're right that neither "ajross" nor "bjross" should be the moral authority who dictates the moral values. That's because they're almost certainly wrong about some things. You're almost certainly wrong about some things. I'm definitely wrong about some things, and I really hope I find out as much as I can about what I'm wrong about as soon as I can.
Therefore it would be a bad system to set up any one person as the moral authority. Instead, we want a system such that over time, the objectively better views dominate and the objectively worse views shrink in influence.
A total free-for-all where anyone can say anything and any kind of engagement will help promote those views, like 8chan or Gab, is clearly not such a system. You don't think a careful implementation of "tolerating anything but intolerance" could possibly be such a system, and is in fact a "far worse evil"? What rules do you think there should be, or do you think a free-for-all with no rules is the only way to not lead down the "slippery slope"?