Hibari's been a subject of discussion at one point of the conversation basically every time Shun and Ren have met so far so while Shun hasn't met him he has a pretty good idea of how difficult he is to deal with. Once he gets over being pissed with Eric he'll probably sympathise at least a little. dw he'll just say it out of hibari's earshot
he'll start a fight on his own terms but not if it's going to get someone else's ass kicked for something he said