In my own experience it's possible to tell people anything as long as you're friendly and strike the right tone. The key is to not get worked up or emotional. Even something extreme like telling someone you don't like working with them - there is a friendly way to tell someone that with a smile on your face
Every unkind "truth" can be wrapped in the right packaging. The usual crux is to not get emotional and not get worked up and to lay out the facts, no matter how painful, in a way that shows you're not boiling over
On a team level I'm not sure what you can do. Especially with a group of low EQ nerds :). Maybe if one or two people set the examples then it's easier for others to catch on?
