Usually, tokens for bounty hunters is only-1-3% of sold tokens so I don't think only bounty hunters are guilty of the price drop.
Tokens earned by the bounty hunters are rewards for their work. So to keep or sell their tokens is only up to them.
I am keeping coins I received from bounty only if I am sure that coins are undervalued.
For some bounty, I am selling coins immediately once they hit exchange, but I am never selling all of them, I am always keeping small part, because in this crazy crypto world who knows what will happen in the future.