Are you suggesting that Haidt is in fact an expert on youth mental health? What do you base this conclusion on? Him having written a bestseller?

While you are right that Wikipedia can be biased, I'm surprised you bring this up in this context.

It's not hard to objectively evaluate a professors research expertise. You look at the scientific papers they have authored.

That's about as far from a bias-prone topic as it gets. I get maths is even less prone to political bias.