I don't know. I think you can tell someone you disagree outright and still be nice about it. I've been in situations where people act like how you're suggesting (i.e., frame the issue as being with them, instead of with me) and it comes off as a little passive aggressive. I know that might sound odd, but in the end it makes me feel like they're hiding something from me or not willing to tell me what they really think.
I feel the same, but I think we must admit we are weird. Most people do not want to hear what other people really think, and you most certainly should not assume that people usually have such desire.
