I don't think there is an effective way to stop dumping... you can try to make it more difficult, creating buy walls on exchanges, distributing tokens only after some product has been presented (this would have to be close to the token sale), announcing exchange only after the project has something to show, etc....
but in the end only people's trust on the project (and this depends on many things), and evolution of reasoning on the crypto-holders (start to think and don't get driven by the quick-cash) will change the scenario...