It's last Sunday. I'm standing at a bar. I'm hungover, so I'm just kind of staring into space, waiting for my Bloody Mary. Two women come up to the bar. One of them turns to the other and says what I swear sounds to me like:
"What's a martini?"
The other cocks her head and looks up and to her left, in an expression of what I swear looks to me like bafflement.
I say:
"A martini is traditionally five parts dry gin, one part vermouth. However many people prefer a vodka martini, which is essentially the same thing, except with vodka instead of gin."
Cue about thirty extremely uncomfortable seconds of confusion in which it is slowly and painfully established that the woman had in fact turned to her friend and asked:
"Would you like a martini?"
This is a 
Who has a Martini for lunch on a Sunday anyway. They where crazy girls. You got off lucky.
On the other hand it's an opening to a conversation and you never know where those might lead.
It's not an opening to a conversation when you say something stupid and condescending. It's an opening to being extremely embarrassed.
Look on the bright side.
You didn't spend half an hour explaining Gibsons, dirty martinis, the shaken/stirred debate, the variance in proportion...
You idiot. Everyone knows the only response to ANY comment about martinis is "Shhaken or shhtirred".