The only good is knowledge, and the only evil is ignorance.

Stated absolutely it goes too far, since plenty of well-informed people do harm on purpose. Read as a claim about causes it holds up better: much cruelty runs on not knowing, on never having met the people affected, on a picture never checked. Ignorance is comfortable and it does not feel like a moral failing from inside. That is exactly what makes it dangerous.

When you find yourself certain about a group of people you have never spent time with, treat the certainty as a signal. Go and find one account from inside it. Most hardened opinions do not survive contact with a particular person.