Step by step, one slips towards the bottom:

1. One should be blunt with those who are wrong.
2. One is blunt when one is right.
3. When one thinks to be right, one is blunt.
4. One is wrong and blunt.

Let's note anyway that one can slip to the bottom without being vulgar or insulting. In any large project like Debian, one can find people who know how to be very oppressive, while keeping a very “correct” communication style. Debian is a broad project, and it is easy to avoid them, unless one tries make contributions that can be related to keywords like “committee”, “code”, “policy”, “delegation”, etc. In that case, it is better to retrieve the good old thick skin from the cupboard where we stored it after our code of conduct was adopted...