MNW's promise was that he will give 100% ROI if pirate defaults. When pirate officially defaulted, he has broken his promise.
Compare to a bunch of tokens / IOUs which has zero terms. No contract unlike MNW, end of story. If I said that I would redeem those for actual BTC, and did not specify a time, then it would have to be a reasonable amount of time.
Exactly why I asked Theymos "If I had made the bet with Ripple IOUs instead, would I still have gotten the scammer tag?". It's a legitimate question that he needs to answer. Apparently scamming expected value, cheating, tricking, promising without delivering, whatever you want to call it-- is fine so long as it utilizes the Ripple system.
I know why you did what you did, I know why I did what I did too. I know I'm not a scammer and I'm pretty sure you're not a scammer. This isn't about you or me, this is about what people classify as "scammers", what criteria Theymos uses to give the tag out (for god's sakes, BFL still doesn't have a tag!), etc. This is about policy, protocol and having a community understanding that it's in fact not okay to play with other people's money to prove points.