Bounty scams like that won't be easily stopped.
the solution is stop promoting and don't just random join a bounty campaign. bounty hunters have often been scammed by a project but for some reason they still carry out promotions without stopping without thinking first (didn't learn from bounty scams before).
so the problem is on each bounty hunter itself. if you feel bored with such a situation (scam) you should try switching to other campaigns that pay using bitcoin or eth. the payment of using tokens is sucks.