I found a blog post about this referrer spam here https://www.billhartzer.com/pages/how-to-filter-referrer-spam-in-google-analytics/ and a discussion about it here https://productforums.google.com/forum/#!topic/analytics/3Z70LrrdS4Q
Actually, I think this is the best way to filter out the referral spam: https://support.google.com/analytics/answer/2795830?hl=en Click Admin in the menu bar at the top of any page. In the ACCOUNT column, use the dropdown to select the Analytics account that contains the property you want to work with. In the PROPERTY column, use the dropdown to select a property. Click Tracking Info. Click Referral Exclusion List. To add a domain, click +ADD REFERRAL EXCLUSION. Enter the Domain name. Click Create to save.