@aral People who feel like they're being told they're bad people with bad intentions are going to be less inclined to do what other people want.
It doesn't matter if you're right; if the people who you're trying to convince think you're a jerk, the people who you're trying to convince won't want to help. I've had to learn that lesson a lot of times.
You can't control other people, you can only control yourself, and how you treat others.