To unfriend a supporter, click on the "send a message" icon in front of a supporter on the Leaderboard/Friends screens or on the bottom toolbar of their post. (Newsfeed > Remove from Friends.) You will no longer receive any messages from this supporter. You can always go back and friend that supporter again in the future.
You can use the same steps to block a supporter, the same way you did to unfriend one. The difference is that if you block a supporter, you will never again see the individual's posts and profile again.
BE CAREFUL when you use the block feature! If you block the wrong person, please, send us a request at firstname.lastname@example.org and we will solve the issue.