It causes genocide? Or it doesn't help prevent it? Those are 2 different things. It's unclear to me how Google's absence from the Chinese market actually ameliorates your concerns regarding Tibet.
It doesn't ameliorate them, because it will be censored anyway. But when Google goes there and does the censorship, they are complicit in covering up that genocide. And yes, that makes a difference - ethics isn't about pure utilitarianism, at least not for most people.