Overwhelming majority of the people who study math do not troll each other over disagreements.
Overwhelming majority of the people who research science do not troll each other over disagreements (although they do have occasional heated discussion).
Even programmers will have occasional flame wars, but for the most part, they agree on overwhelming more than they disagree on.
Overwhelming majority of the people who practice law have norms on how to remain civil even though the legal system is adversarial.
Overwhelming majority of the people who engage in politics, in any way, troll each other. They make statements which they know to be false (but which they know may sway some people's opinions). Swaying opinions is the name of the game.
Now you have a site dedicated to studying politics as if it were a subject rigorously isolated from people's own emotional attachments. And the format for the site is the same as the format for other sites dedicated to studies in which disagreements are simply not as common as they are in politics.
And yet you are surprised that it does not produce the same results as those sites. It's because the subject matter which is being explored is practiced by trolls. Can it be studied without revealing everyone's own biases (which is what's necessary to keep it rigorous)?
To most participants it will present the Prisoner's Dilemma. Remaining rigorous, in the face of other reputable members acting like practitioners of politics, rather than like students of politics, feels like being the sucker in the Prisoner's Dilemma. So eventually everyone does from time to time descend into the gutter.
Even the moderators are not immune. Again, this isn't because the site lacks rigor compared to the other SE sites. On many occasions it's more rigorous. It's because the subject matter is practiced by trolls.
I am sorry if this doesn't feel like an answer, but in order to avoid a lack of rigor, you need different rules from the rules which guide studying of other subjects which are not (overwhelmingly) practiced by trolls.
Alternatively, you can follow the solution to this dilemma which was recommended by Joshua (of the movie War Games): the only winning move is not to play.