Because maybe those many nice people couldn't program their way out of a wet paper sack.

If I'm looking for someone to go to a bar with, I'll pick the nice person. If I need someone to help me complete a project at work, I'll probably try to find someone who's good at what they do, regardless of whether they're an asshole or not.

You can do that but these people that act like jerks or asshole really do alienate and demotivate others, so while you might be able to handle them if you have a group of people an asshole can really destroy productivity.

That's very true, an asshole can wreck productivity. But we're human beings, and we excuse deficiencies in one area for excellence in another. If the asshole produces more than he destroys, it might be worth keeping him on board.

ymmv, and all that, of course.