I've been around countless athletes/drivers/etc. in my life. Owned a company that did very high end auto customization, the pro athlete was our best customer.
They all have one thing in common -- they are all incredibly competitive people. But they don't all have the ability to turn that stuff on and off. Some of them can be friendly, warm and welcoming one minute and the next minute they're ready to compete at a world-class level. Others, it takes hours build it up and hours to come back down. And still others don't know any other way -- would race you to that soda machine over there.
Not sure where Kenny falls, but my personal experience with him is to steer clear of him at a race track. When he's wired, he's not a nice guy. But that's just my experience.