An absurd and possibly dangerous concept/cult where it's believers have a total rationalized license to verbally abuse those they wish to alienate from their lives. It is used selectively by some and wholly by others. If you've read the books or paid hundreds or thousands of dollars for the workshops, then you have even more license to be cruel and you will be taken more seriously by the other Radically Honest Cult Members. There is no place for diplomacy or kindness if you're a believer.
Wife: "Honey, do I look fat?"
Husband: "Yes bitch, you look hella fat because you ARE fat!"
Johnny: "Mommy, do like this drawing I lovingly made for you?"
Mom: "No. It's ugly, I hate it, you need art lessons ASAP, son!"
I'm just giving you some Radical Honesty! F off if you can't dig it! It's just how I roll, yo!