Frank, before you pose that question maybe you should decide what penalty he should serve since you've already determined his guilt. This surprises me Frank as you usually break stories not act as judge.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .