A more interesting question is: 'Are unicorns good for the economy and good for society'?
Are: eBay, Amazon, Google, Facebook, Uber, Priceline, Expedia, SpaceX, Tesla, PayPal, FirstSolar, GoPro, Salesforce, Workday, FireEye, Splunk, Netflix, Yahoo, Twitter, DropBox, Palantir, Pandora, etc. good for the US?
They were all the equivalent of small unicorns once. So the question is: as opposed to what? All of those companies existing somewhere else, and most of the benefits going to other nations instead (jobs, taxes, investment, innovation)?