Startups aren't a zero-sum game. If you're in direct competition with a YC startup, the synergy might hurt you (though everyone says not to worry about competitors anyway). But if you're not going after the exact same segments of the same market as a YC startup, their success isn't hurting you one bit.
By definition, if start-up x has an advantage over y, y is disadvantaged relative to x. With all due respect, I don't mean to argue over minor things or 'knock' yc. But surely this is a statement of fact. If not, please prove otherwise.