I've managed to keep from being incessantly downvoted in my unpopular opinions by providing well documented arguments (logos, with an occasional appeal to ethos of sources), tying to personal credibility or experience (ethos), or providing personal experience developing an empathic response, then tying into into the main argument. (pathos -> logos, or just pathos.) The problem isn't disagreement - it's not developing…
Well thought out arguments don't matter; we are supposed to downvote anything we disagree with: http://news.ycombinator.com/item?id=117171 (from pg himself).
Either way, as I've mentioned before, guidelines are just that: you can't force someone to not downvote inappropriately. It's just the nature of this sort of community. I think if people focussed more on not posting things that are out of line that get hella-downvoted instead of worrying about whether they have hit four digits of positive karma, things might be a little more laid back and people wouldn't stress so much. Either way, as long as there is karma, people will bitch about it one way or another ;-)
(Note: not dissing four-digit karma. If you have that much, you've earned it. Just saying that maybe people worry a bit too much about getting positive karma instead of avoiding negative karma.)