The people who have certain knowledge of something wrong in the world, through firsthand experience or domain expertise, should certainly speak out. For example, I'm vocal about accessibility for blind people, perhaps to a fault. But I think we should be silent about things that we don't have direct knowledge about. Otherwise, we're no better than computers in a botnet sending out spam. That's why, lately, I've unsubscribed from multiple political mailing lists that keep pestering me to sign this petition or talk to my legislator about that important issue. I realize that I don't know enough to have an informed opinion on these things, and I don't want to be manipulated. (Yes, the fact that I unsubscribed implies that I went through a period where I was more involved in things I don't have expertise about; I was wrong in that.)

>The people who have certain knowledge of something wrong in the world, through firsthand experience or domain expertise, should certainly speak out.

To whom? If everyone followed the rule you're proposing, the only people they could speak out to are people who share their firsthand experience or domain expertise. Communicating further would necessitate secondhand information or some form of media which can't be trusted, as it could possibly contain some manipulating element. Who could Ukrainians ask for help from? The Russians? Would everyone else be required to fly to Ukraine to try to verify the existence of the war firsthand before having an opinion?

There are more important things than being made a fool of sometimes. The risk of being manipulated exists no matter what you do, or don't do, and you can never have perfect knowledge of any situation, even if you're an eyewitness, because human perception itself is fallible, limited to a single perspective and prone to self-deception.