You can’t use the full power of government sanctions and criminal charges to silence the people you disagree with (for whatever reason. Even if they are valid reasons) so you try to find creative ways to punish them. Well… not really “creative”, since the idea of excommunication is not new. But my point is that this is still about using power to silence voices you don’t like - you just use a slightly different power in a slightly different way.
You want to silence certain voices (the one telling lies) but can’t/won’t use proper government sanctions, so instead you coordinate the community to keep distance from these voices, hoping to deter people from voicing them and preventing the ones too determined to be deterred from getting any reach. This is excommunication.
My problem is not with the exact way you are trying to censor your political opponents - it’s in the very fact you are set out to censor them. You don’t have to listen to them, you don’t have to give them a platform, but if you try to establish a wide system to prevent other people from hearing these voices - that’s censoring.