I think the 'controlled opposition' comment is pointing out that given a choice between doing the right thing for users vs. keeping Google happy (presumably to keep the search money comping in), they often seem to choose keeping Google happy. So while Mozilla has generally been less bad for user interests, it's still often far from being an advocate for them.
And yet it's devoid of truth. How many times has Google proposed some ridiculous new API that Mozilla has immediately and publicly rejected, often with strong language? I can count at least 2 off the top of my head from the past year alone.
