That's (tautologically, I admit) defined implicitly by my answer. I define it (for the purposes of this conversation) as an opinion that its holders buy into s

That's (tautologically, I admit) defined implicitly by my answer. I define it (for the purposes of this conversation) as an opinion that its holders buy into so much that they outright refuse to acknowledge anything in opposition. After-all, if you believe you've bought-in to "the truth" (and lack critical-thinking skills, and/or have been propagandized to this point anyway) then it has to be an extreme position (by whatever the standards of the contemporary Overton window apply) because otherwise it wouldn't be necessary to propagandize or rile similarly-minded people against your opposition.