The following argue in favour of negating positive words
(e.g. This has not been agreed; allowed; correct; considered.)
to evade single negative but polite words
(e.g. This has been disagreed; rejected; wrong/false; ignored/neglected.):
Avoid negative words - instead use positive words in a negative form
People react to positive sounding words, even if they are used with a negative auxiliary verb.
Don't say: I think that's a bad idea.
Say: I don't think that's such a good idea.
Avoiding the negative
- I don't think that's such a good idea. (NOT It’s a bad idea.)
- I don't think I can agree with you. (NOT I disagree with you.)
- I'm not sure it's the best idea. (NOT it's the worst idea!)
But I disagree: the former looks needlessly periphrastic, indirect, circumlocutory); I prefer the latter's concision. Am I wrong? Is the latter really less diplomatic?