I finally found out where Hangouts got the Contacts it added to my phone. In addition to GMail I also have a hotmail account. I was sent an email to my hotmail account that had a large distribution list. Well, Hangouts copied every email address from that distribution list to my phone, and, I could not delete them. Also, Hangouts looked in every folder in my Hotmail account and copied every email address it could find, some as old as 10 years, to my phone. Hangouts copied approximately 500 email addresses and put them in my phone as Contacts. I did not know Hangouts would do this; now I know!! So, if like me, you're going to give Hangouts a trial run, beware.
I was finally able to delete the contacts added to my phone by going through all my hotmail folders and deleting all my old emails.
Jim