One very important thing to counter hate is to try to have everyone in society involved in society somehow. People are much less willing to wish ill on others in society (or society itself) if they feel that they are part of it. A lot of stories about people being radicalized start with a person feeling at end of the rope and alone.

This isn't something that you can really do online, but it is something that can be done in real life and should probably done more. Friends are a powerful force.