I think we are all plant-growing maniacs, and most of us have the banana-growing addiction.
I'm not an Obama lover, a Tree hugger, a Bush fan, a chemical Farmer, a Romney recruit, an irrational Organic, or a Newt tooter. Occasionally I read an opinion I don't agree with. I'm not going to block anyone because they have a different opinion -- heck, I might learn from them.
I think what we're talking about here are people with persistent, baseless, emotion-driven opinions interlaced with name-calling and personal attacks. Generally if you don't respond they go away. In some cases you might have to add them to your "ignore" list but that's pretty extreme. Sooner or later people stop responding to them and they go elsewhere to get attention.