Yelp is evil (imho). So why does Google weight them so heavily?

I'm nearly fed up! I've been working to get more Yelp reviews onto a friend's Yelp business page. I've been emailing prior customer's of his, he's been passing out cards to customers asking for their review, etc. The reason he's doing this is because a "customer" he's never met before left a negative Yelp review, so he wants to combat it with positive reviews.

In regards to my emails I'm sending, I know some customers are clicking the link to his Yelp page because I'm tracking the clicks however NO positive reviews are making it onto his Yelp page.

I know Yelp blocking reviews is nothing new & frustrates everyone, but I then wonder, if business owners feel it hurts their business in a shady way, why doesn't google place a penalty on Yelp to lower their rankings? Why is Yelp still weighted so heavily on Google? Just one google search for services for fixing bad Yelp reviews should go to show how negatively this site hurts legitimate hard working businesses.

Is there anything I can do to help get these reviews into Yelp? Is there another way?

Sorry if this sounds more like ranting. I'm just fed up at this point!

Thanks