Sometimes there is a need for sarcasm.
I find it very rude when people begin by lecturing a Working Group on the 'fact' that nobody understands the subject matter. This is not the exhibition of modesty etc. that it pretends to be, it is actually a trap designed to gull the WG into agreeing that they know nothing about the problem whereupon the original proposer will gladly provide the poor naifs with their pearls of wisdom.
The correct response in such situations is in my book, 'you may speak for yourself and your own level of expertise but do not accuse others of sharing your inabilities'.
I also find it very rude when people try to cut short a discussion with recourse to bogus points of processor try to trump a discussion with recourse to an authority that I know from private conversations to hold the exact opposite opinion to the one being attributed to them.
What I found incredibly rude was when an AD and Working Group chair actually hissed when I gave my company name at the mic.
But what I found worst was the fact that nobody seemed to be taking any notice at all of the four women who raised diversity issues at the mic in Orlando until I got up to the mic and mansplained the issue for you all.