The presence of slurs absolutely acts as gate keeping, Poal is an excellent example of that. But it's dangerously repulsive to most normal people. It's like having an anti-abortion forum that forces each member to regularly watch a late-term botched abortion, or to watch a baby be left to die on a table. Yes, it gatekeeps, but it's also fundamentally awful, even to those who agree with you, which damages the possibilities of growth.

Trolling in moderation yes. It's why Haterjuiced managed to keep himself from getting banned. Flame Wars, no. Flame Wars don't serve a good purpose beyond damaging the forum generally with hate & discontent among the users. There are no moderate Flame Wars anyway.