I have no problem at all with people letting their conscience be their guides when deciding what products to buy or services to use. For example, I certainly wouldn't patronize a place like Portland's Red And Black Cafe due to the way it refuses service to police. To me, though, it's a completely different thing to organize groups to punish people for the express purpose of silencing someone merely because you disagree with them. It smacks of the fascistic, and while it doesn't rise to the level of a First Amendment issue, private citizens not being the government, it is still wildly out of step with the spirit of free speech that is a cornerstone of our nation.
There already exists legal remedies both civil and criminal to deal with speech that is actually harmful. Libel and slander suits, false advertising, inciting to riot, etc., are there for the purpose of protecting individuals and maintaining order. These little vigilante groups running around trying to impose their idea of "allowed" speech through financial extortion are distasteful in the extreme to me. They are definitely not people who understand what America is supposed to represent. They would counter that those same American freedoms are what allows them to do this, and I would agree with them. I don't question the legality at all, just the motivations behind it, which I think are obvious.