I don't think there should be legal consequences to spreading misinformation.
No authority should exist that claims to know and decide what is truth and what is not.

If there are any consequences to spreading misinformation should exist, they should be verbal, not physical, not material.
You can tell them they are wrong, you can walk away from them, you can deny to associate with them.
Doing anything that physically or materially harms them would be unethical and unwise.