What I'm not fine with:
"This is crap" (without pointing why or how to fix it - of course with ruder words)
"We're not applying this fix" (without any explanation why and the system is pretty much broken/only works for limited cases/bug waiting to happen/etc)
"What are you talking about?"/patronizing behaviour (when it's crystal clear what you mean)
And usually the ones with thinner skin are the ones who try to push fundamentally bad things.