Varying degrees of politeness

Disagreeing:
1. But what about...,
2. Shouldn’t we consider...
3. Don’t you think it would be better...
4. I'd prefer...
5. I'm afraid I don't agree...
6. I don't think that...
7. I don't agree.
8. The truth of the matter is...
9. Frankly, I doubt if...
10. Let's face it,
11. The problem with your point of view is that...

Variations 1-3 would be most acceptable with people, regardless of social status, gender, or age. These phrases signal mutual respect, and would most likely be used by a subordinate. #4 is actually stating a preference, which is a little more assertive, but still shows deference towards the listener. #’s 5 and 6 would be acceptable (and respectable) for those of equal social status, without regard to gender or age. It would probably not be acceptable to use these phrases with a superior unless a good relationship has been established beforehand. #7 is ok across the board if the speaker can provide sound reasoning for their disagreement. #’s 8-11 would most likely be used by a superior speaking to subordinates, or in an adversarial situation, such as a negotiation.

On the “More Polite” end of the spectrum, the speaker uses softer phrases, which emphasize the need to work together and to consider alternatives. Moving towards the middle, the speaker is showing respect for the other person’s opinion, but is becoming more assertive, stressing the need to consider the opinions of each other, rather than to work towards a common goal. Towards the “Rude” end, the speaker is making it known that his opinion is the only one of value, stressing the listener’s incompetence/lack of understanding.