Language is full of color - and I find it a disservice to desaturate those colors. The bright are made all the more brighter when contrasted with the dim.
By muting language you make it harder to distinguish between those colors. Polite language becomes aggressive and disliked because you know when it is forced and dishonest and when everyone is expected to be polite - you lose the ability to distinguish between the forced politeness and the honest politeness. You begin to treat all politeness as forced politeness.
If you've ever been in a "100% optimistic, go-positive attitude" environment for any length of time you learn to hate it and treat everyone there with contempt. Being able to express negativity is important.