Is that just a flat out lie?
Maybe not outright extortion but certainly not what they claim of being a truly independent forum.
An environment where salespeople feel they can do stuff like that is a problem, but no, it is not proof that "yelp deleted bad reviews for money"
Yelp definitely hides a lot of reviews that are completely legitimate supposedly due to their review validity system filtering them, but in a lot of cases I've seen the only crime these disenfranchised reviewers had was that they didn't want to go make a full-blown Yelp profile with pictures and everything to make really serious, very well described complaints. This artificially inflates review relevancy ratings for companies that have Yelp reviewers that skew towards younger demographics. There's a ton of stores where I live that are frequented primarily by 50+ year olds but they have almost zero Yelp presence since nobody operating or visiting the store are much into technology / social media enough to care.
There were also complaints about ridiculously high security to the point where people didn't even know their own exact job descriptions/workflows because of "competitive secrets" and that they couldn't talk to people working in other departments due to paranoia/culture of fear.
Finally there were a couple about how they interview and act like your job will be at the fancy building on Sand Hill near Stanford but really the bulk of the employees are relegated to annexed buildings far away in EPA or in Mountain View, yet they don't tell them this until their start date - during all their onsite interviews up through the offer letter it seems like they'd be working at the HQ on Sand Hill.