There's a world of difference. For Mozilla to sell out on user's privacy it would mean game over. They simply can't afford to do so, even if they wanted to (which I believe they don't). Google on the other hand? That's their main business, they are an advertising agency. Sure they make nice products too but make no mistake where their profit is coming from.
But if a substantial portion of Mozilla's funding comes from an organisation that does have a profit motive to monitor and monetise my activity on the web, then surely that's almost as bad (for me as the end user)?