There are economic losses suffered in every pump and dump. For you to gain value, someone has to lose value. This lost money could've been invested in cryptocurrencies that actually have a legit project and good potential, which in turn further supports the development of the technology behind the legit project. The tokens of the legit project would be worth more. As a result, donations for its development are worth more, and its network effect is larger.
Furthermore, many deception tactics are used to raise the token's value in pump and dumps, and this along with losing big in a pump and dump can really turn people off of crypto in general. So much so that it can cause them to never re-enter the ecosystem. Cryptocurrencies as a whole are still early in their lifespans, and they can use all of the allies they can garner.
Be a part of the solution, not part of the problem. Those that say they care about the technology and knowingly participate in pump and dumps do not truly care about the technology. They are effectively scammers because they knowingly support and participate in pump and dumps where greater fools are fleeced of their money.