Linus Torvalds apologizes for his behavior, takes time off
Linus is stubborn, persistent, and unyielding to what he sees as bullshit. These I believe are all very valuable qualities for the head of a massive software project, and may be part of the reason as to why Linux is where it is today.However, Linus is also a bit of an asshole, turning technical criticism into personal seemingly personal attacks. I believe those 2 sets of qualities are separable, but I would guess it's uncommon to find many people who are capable of being as tough as Linus without in some way alienating those around them, it's a fine line at times.Anecdotally, one of the most effective engineers I worked with, who asked penetrating questions during code and design reviews, did come off as a bit of an asshole at times. Whether by genetics or through childhood, I'd bet people tend to cluster onto the line separating "agreeable and lax" and  "rude but firm" (as a sweeping generality). We often label people who are all smiles while simultaneously extremely strict as passive agressive. Add to that the fact that many technical people are less socially adjusted than average and I can see why we have so many examples of mean but effective project leads.