Tired of receiving messages from someone on Facebook and do not want to start any conversation with them, then you can unfriend using the option available as part of the Privacy Shortcuts.
Step 1: Login to your Facebook account and click the privacy shortcut option on top right hand corner.
Step 2: Navigate to “How do I stop someone from bother me?” option and expand it.
Step 3: Now enter the name or email address of the person and click the Block button.
This would prevent that person from starting conversation with you and seeing the details on your timeline.
And if you wish to unblock the user then you can use the option available as part of View All Blocked Users.