I've read tons of advice on the subject, which boils down to understanding their motivation and therefore not being offended by the modus operandi of the jackass. I can understand all day, but that doesn't make facing such a person any easier.
Admit it. There is stupidity, arrogance, and envy in the world, and some people operate from one or more of those almost exclusively. We all have to deal with those people to some degree. They may be coworkers, customers, even relatives. They may show up at your church, in your doctor's office, at your home.
Although opinions about who is insufferable vary, my least favorite people are arrogant and self-absorbed. Only their opinions matter, and they insist on sharing them with you, incessantly.
My defense mechanism is to flee. I find myself unwilling to make eye contact, keeping my responses to an absolute minimum, and getting away ASAP. Now here's the ironic part. I'm aware that such behavior convinces certain people that I am self-absorbed and arrogant, even rude. So guess what: I'm in all likelihood a person that someone else can't stand.