I was sitting in Starbucks, sipping a tall bold (no double-caramel-cinnamon-latte-half-decafe-two-percent for me). Some retro album was playing over the sound system, Frank and Nancy singing "Then I go and spoil it all by saying somethin' stupid, like I love you."

A couple of guys walked in and sat down at the table across the room. I didn't pay much attention to them until they both opened their laptops and started playing music. Neither had earphones apparently. Or if they did, didn't feel the need to use them.

Now, Dean Martin sang "On an Evening in Roma" to the semi- syncopated and monotonous beat of techno coming from one computer, and rap from the other. When one of the guys found a song he particularly liked he'd turn it up so the other (along with the rest of Starbucks) could hear it better. Several people moved to other tables. I was far enough away that it was only an irritating background buzz, something akin to a mosquito with rhythm.

There was one fellow I'd seen before, who sat right behind these two, reading a book, Spinoza I think. He sipped his drink casually, yet seemed focused with Zen-like concentration on his book. While the rest of us cringed when they got up to get refills, realizing that this meant the impromptu concert would go indefinitely, he seemed immune.

Eventually they left. The barista came by and wiped down their table. I nodded at the guy reading Spinoza. He nodded back.

"I'm impressed with your patience," I told him. "Why didn't you say anything to them? Ask them to turn it down?"

He shrugged. "Do you know what a psychopath looks like?"

"No."

"Neither do I," he replied, and went back to his book.

I thought about that for a while. He was right. You can't tell what a psychopath looks like any more. All the best serial killers, or at least actors who play serial killers, got the part precisely because of how normal they looked: Anthony Perkins (Psycho), Christian Bale (American Psycho), Michael C. Hall (Dexter). You can't tell the difference just by looking.

Consequently, we have let the rude cut in line in front of the rest of us. When they step over the line, we don't say anything because they might have just been released from the psychiatric ward, the state penitentiary, or worse, are a card-carrying member of the NRA.

We all know where the line is and when they've crossed it. It's that moment when their rights completely supersede the rights of the rest of the human race.

If they want to blast their eardrums into oblivion by installing a dozen woofers in their trunk and cranking the base so high it disrupts the radar in any plane unfortunate enough to by flying overhead, that doesn't concern them. They don't care if it causes your dog to start howling when they drive by your neighborhood at three A.M.

If they just have to get off at that exit, cut across three lanes of traffic and cause the driver of that school bus full of first graders to swerve onto shoulder, they're unconcerned. At least they didn't have to drive the extra mile to the next exit.

If they get a call at IHOP, and feel the need to yell into their cell phone, since that little microphone hole is so small, causing their words to carry over every other conversation in the room, it's a sacrifice they're willing to make. Afterward, they stare at you with that accusatory look that says, "You weren't eavesdropping, were you?"

Unfortunately, there's no reliable way to tell the difference between the pathological and the run-of-the-mill rude - other than confronting them and waiting to see if rudeness will escalate into knife-wielding rebuttal. Life would be so much simpler if all serial killers wore hockey masks in public. I guess I'll get a copy of Spinoza and start boning up on my Zen.