That's wrong. Sometime, you know you have a valid point and will get down voted because people won't spend the time to understand correctly your meaning. By saying it before hand, people will understand that you know it's a bit of a controversial subject but still spent the time to make your point.. and thus, won't just down-vote you because they thought you were wrong at first glance.
Heh, I know how true that is, but I think it's healthier to look at it in a different way: if I have a valid point but people don't understand it, it's my fault--I did not write clearly enough. I take it as a signal that I need to sit down with that idea and work out exactly what I mean as opposed to what I say.
Of course, there are always exceptions: missed allusions, overlooked subtleties and well-reasoned but unconventional points can be downvoted incorrectly. However, most of the time, it's healthier to think of it as your fault.
http://raganwald.posterous.com/youre-probably-going-to-downv...