Apologies for not finding citations, but as an example of... suspicious behavior... Firefox had a big campaign about blocking Facebook tracking with a big push to install an addon to reduce Facebook data collection. They did not do that with Google. That's the one that stood out to me as especially asymmetric, others may have other examples they remember.

Don't get me wrong, Firefox is clearly the best of the options available. I use it all the time. But I'm also very aware that there is a bigger bias against Facebook (don't actually care since I don't go near it and block its javascript and cookies) than against Google. Of course, it's not obvious that this is Firefox's fault, Google is extremely good at finding probably-shouldn't-be-legal workarounds to just about any attempt to retain privacy.

You'd think making clear you want to retain your privacy should be enough, legally, but I guess there are no consequences.