Do you ever have conversations like this? Someone asks what you think about their pet issue. Whatever it is. Then if you gently, politely, ever-so-slightly disagree with any part of it, the following happens: their eyes narrow into slits, they loudly repeat their views in a half-shout/half-hiss, or they ask you some pointed rhetorical question ("Well, that must mean you are one of them, right?")
Now, here is a pop quiz: What do you think of the other person's viewpoint after this exchange? Here are three choices:
a) You are suddenly transformed and now see the wisdom of the other person's argument.
b) You appreciate the chance for a frank exchange of ideas.
c) You are silently whispering to yourself, "OK, take three steps back from the crazy person and don't make any false moves..."
It isn't just individuals who fall prey to this. Try donating to a political party some time – any party – and then start reading the breathless letters they send you about those awful, horrible people on the other side who will stop at nothing to completely ruin life as we know it – unless you send us more money. (And obviously it doesn't work because next week, by golly, they are at it again.) I often wish we could lock the letter-writers from each of the major parties together in a room sometime and watch what happens.
Of course, unless you happen to drink their particular Kool-Aid, all of these people are about as persuasive as spam e-mail. And many of them don't even see that blurry line where their passion for a cause or an issue turns them into boors who can no longer discuss it rationally.
Most of us need to form opinions in our own time and space, and proselytizing scares us off. If you really want to influence me, learn to have a respectful two-way dialogue that understands other viewpoints, because that is the only way minds are ever really changed. Otherwise you will preach exclusively to your own choir, and your passion will be completely wasted.