This is stealing and the behavior of the owners/operators is outrageous, in my opinion. That policy is completely unjustifiable and I hope nobody uses this site until it's changed.
What's the best way to organize a boycott / raise awareness?
If you want to raise awareness, just link to the BitBet FAQ,
which is public, which you should have read before sending 10 btc anywhere.
The inability to own one's actions on this forum is at absurd proportions. read the rules of gaming websites before you place your bets. is that so insane?
If I pick up someone's wallet off the street, is it right for me to spend money from the credit card inside of it?
That's essentially what Bitbet is doing, except they know exactly who the money belongs to and have every opportunity to return it. They can write in their FAQ that it is ok for them to kill anyone who loses a bet, but that doesn't make killing someone who loses a bet right or legal.