Yelp allegedly--and while I believe it it has not been established--burying positive reviews for non-advertisers isn't a crime (in the general case; your jurisdiction may disagree, but extortion etc. are, to my layman understanding, almost strictly limited to threats of violence). On the other hand, Uber is, if the allegations are true (and they've copped to Grayball), obstructing justice on behalf of third parties. This is an actual crime.

If you believe that Yelp should be barred from preferential reviewing in your jurisdiction, talk to a legislator. (I would agree with you and vote to that effect in my own.)