I wonder if you turn this around, could every body have a tendency to be nasty 5% of the time?
But that's different. There are people who are nasty more like 50% of the time, or maybe even 95%. It's good to recognize that yes, that's me some of the time, but "quantity has a quality all its own", as Stalin (allegedly?) said. Too much of that attitude and/or behavior puts you in a different category.
And even for people in that category, it's also important to realize that they have their 5% - or even 50% - where they aren't like that. That doesn't make you want to hang around them - even 50% jerk is too much for me to want to spend time with them - but still recognize that the other part is there, and appreciate it when you see it.
Riffing off of the author's restaurant example: at the restaurant I worked at in college there were "known nasty" regulars. They were just...always horrible to the waitstaff. The hosts knew not to seat them in the veteran servers' sections, so I often dealt with them.
If they did happen to get seated in someone else's section, they'd get pawned off. Even the one waitress on the team who was constantly hustling to work every last table/shift/upsell she could manage would hand them off to me and let me keep the tip (if there was one...), rather than having to interact with them herself.
If this was a general rule, it would be easily noticeable, and I haven't seen this in people I interact with.