7 Minutes with 6 fingers and the Big Guy

I had the most absurd visit to Dunkin' Donuts the other day.

I go in and order a plain bagel with plain cream cheese and a large latte. Ordinarily I would get a black coffee, but I had just received news that I was hired for this position I really wanted, so...actually, I don't know why I'm explaining my need to treat myself.
Anyway, apparently you cannot simply get a plain latte. You must choose out of 70 plus flavors and then specifically ask for it to be "hot" instead of iced or cold or whichever other temperature they use for coffee these days.
Yes, I know that part was annoying, but it had to preface this:
While the man behind the counter is endlessly listing espresso flavors, this guy behind me begins to sigh really loudly and continues to bemoan and for the 30 second wait through which he must suffer. I was perfectly content with hearing him obnoxiously mutter, "Come on!" until he says, "Don't you know what kind of latte you want? It's really not that hard! Jesus!"
Color me PISSED.
Without turning around, I retorted, "Take it easy, big guy. You'll get your coffee!" As I turned around to complete my response with an icy glare, I saw my main offender. I was right, he was a big guy. A big guy. Huge. I felt terrible. I call people "big guy" "man" "dude" "champ"...any number of things. I've never had it backfire on me like that before.
I turned back around with my mouth open only to realize that the guy handing me my bagel had six fingers. He had a smaller thumb attached to his regular thumb. The small thumb even had a nail. My mouth opened wider.
Two things make this situation more absurd than it already was to begin with:
1.) My librarian friends and I always joke with each other if one of us is dressed as or behaving like a stereotypical librarian. Well, folks, that day I looked like no one other than your local prudish librarian. Which may or may not make what I did on my way out even more ridiculous -
2.) I stuck out my tongue. As I was leaving, the "big guy" gave me this horrible sneer and narrowed his eyes at me. So, I behaved as any other middle-class, educated, decent human being would. I stuck out my tongue at him. It was like instinct. I still have no idea why I did it, but the toddler in me seemed to have a quicker reaction time than whatever etiquette I've been taught. Ultimately, I don't regret doing it, but it's just curious to me how I did it without really thinking.

I think what pisses me off most about the situation is that I pride myself in being a really accommodating customer. I've never sent food back, I tip really well, I don't complain about waiting, I (usually) don't even think twice about picking hairs out of food and continuing on. Seriously, when it comes to serving me: I'm a dreamboat. So when someone else displays absolutely asinine behavior for no reason at all other than the customer in front of them is listening to their choices, I see red.

In a perfect world, I would've just gotten a black coffee. Then again, in a perfect world, the guy serving me wouldn't have had three thumbs.