Removing a Contact from Messenger

A person contacted me in Messenger about a product I was selling. I no longer wish to have him in my Messenger list, but I can't find any way to delete him. Previously, I was able to add a person to my Contacts and then there was an option in Messenger to swipe and remove unwanted contact in Messenger, but that doesn't seem to be available any more. I would like to remove him both from my MacBook Pro Messenger and my iPhone 6s.