ETH prices cannot be affected by scammers. I think they are just sand grains on a sandy beach. They hold a small amount of eth compared to the amount of ETH being circulated on the market. Prices will not change much when they sell all
It depends on the amount of money that scammers are able to steal, obviously a scammer holding a couple of ETH will do nothing to the market but if they are able to steal the funds of an important ico as it has happened in the past then we could see the price of ethereum suffering as they sell those coins in exchanges or try to sell them through other means, however as long as you do not panic as one of those crashes is happening you have nothing to worry about even in the event scammers get access to so many coins.