People have been able to build successful organizations without being abrasive dickheads to their colleagues and subordinates all the time. I think it's a false dichotomy.
Leaders of large companies are _usually_ more aggressive, selfish and less agreeable than average people. This is a well-researched topic (and also makes sense intuitively -- leading a Fortune 500 company comes with so unique perks that there's an immense fight for those roles).
They do have awesome and well mannered leaders but most are connected to Mozilla.
I'm not sure why it has to be this way or whether it has to be.