You can be super nice and not upset anybody without compromising on technical rigour.
> The problem is that people who prefer direct non-bs communication are also usually more emotionally mature and better at adjusting to others.
I would argue this is entirely false. If they can't adjust to others finding their behaviour offensive by not being offensive, they're not "better at adjusting to others". Yes, this is a two-way street, but that doesn't automatically mean everyone has to be comfortable with the guy who swears at you and calls you an idiot for writing a patch they didn't like.
We can have technical discussions without personal attacks, without rude language, without racial or sexist slurs. We manage it at my work all the time, although I for one think I could still do this better.
It's difficult when we grow up in a culture which glorifies violence and "macho" behaviour, where most of us in the field are male and have been told all our lives that we're expected to be strong and independent and assertive.
And honestly, if you can't find a way to explain why an idea is bad on a technical level without offending someone, maybe you don't have a good enough reason to criticise it, or you need to think about it some more to figure out why you don't like it apart from your initial reaction.