He doesn't want Facebook to sell user data, but when the documentary says they don't sell data, he expresses concern about gathering data.

Facebook gathers the data not just on their platform, but by tracking you elsewhere. Also, Facebook sells the use of the data for marketing.

He says it's okay if someone searching for "stem cell storage" sees an ad for Forever Labs, but if they search for "Wankel engine" and land on a car video, Mazda should "absolutely" be blocked from showing an ad with that video (though his next sentence seems to say the reverse).

I am fine with presenting ads next to search terms. I am not ok with marketing based upon a profile that is built for me. I am less ok with it if it is shared between companies, and even less so if it is created by tracking my behavior.

It is ok if Mazda has to work harder to sell cars or if Forever Labs has to work harder to sell stem cell banking. That's how advertising worked for more than a century. It won't mean more revenue for Facebook, as it will mean a lower ROI on their ad service.