A couple quick notes to Pro. You said in the debate description that, "[...] denial of major tragedies like the holocaust, or 9/11 can be harmful to a debate website." In your Round 1, you said, "Do we want a society where people feel threatened to voice controversial opinions at face value, rather than on merit of what they have to say?" What are Holocaust denial and 9/11 trutherism if not controversial opinions? Also, this excerpt from Round 2: "If I want to be told that I am an idiot for believing the thing I do, instead of being explained to why and shown facts as to why, I can just go to Facebook, or any of the million other sites that encourage this behavior." Here's the thing. If explanations and facts do not make the wrong person see their wrongness, I can only hold my tongue or call them an idiot.
A comment on Con's round 2 also. "Let bad arguments and rude behavior fail on their own merits. The voters will sort it out." Not if the voters are rude and receptive to bad arguments.
Having gotten that out of the way, on to the vote. A large part of me wants to because I agree with Con's position and I feel that this may be subconsciously influencing my vote, although I am trying to be as objective as I can. I was not there for the history of Debate.org and Debateart that was discussed, so I can't say one way or the other who was telling the better version of history, but I got the sense that Con's was more accurate. Both Pro and Con did an excellent job at deciding their points of contention, supporting them, and refuting their opponent's. If I broke down every detail of this debate, I would never get anywhere, so I'm going to sum up my reason for voting Con in one sentence. I found their position more concerted. "Do we want a space where ideas can be expressed and challenged openly, or do we want a site that doesn't allow for the free exchange of ideas in a natural way?" Everything Con said fit perfectly into the schema of this one sentence. Pro's case was clearly that tougher moderation creates a more civil atmosphere, but their points did not synchronize quite so cleanly. Maybe that is a minor thing to decide a debate over, but both sides did so well that I had to resort to that as a tiebreaker.
