He's a douche because: as stated, he deliberately drove to that Starbucks to "break the chain." Who does that? He can think what he likes about it being a Starbucks marketing ploy, but to actually get in your car to put a stop to something is crappy.
He's not a douche because: there is an aggression behind some of these "pay it forward" things, certainly not all of them, but there's nothing that kills my generosity of spirit more than an expectation that I'll be generous. I want to feel like it's my idea.
And while I'm playing devil's advocate, let me sound more like a douche/tightwad/**ithead by saying this: I'm at the store buying things for my daughter's new school year, and the cashier says, "Would you like to round up your total as a donation?" Usually, I say "sure." But I was feeling prickly, for some reason, so I (politely) asked, "A donation for....?" She said, "I don't know. They told us to ask, but I don't know what it's for." So I said, "No, thank you."
I don't know. I guess I'm in a bad mood.