not all bounty hunters dump their token instantly after the end of an ICO. I also believe that tokens that are sold by the bounty hunters are just 1% - 5% of tokens from the total supply, I don't think that this small number of tokens compared from the total number of supply of tokens would greatly affect the price of tokens on a market.

besides, Bounty hunters already did their job advertising a company to earn the bounty token rewards. It's all up to them what to do with the rewards they already received.