This will prevent Wilfrid from sending you messages, friend request or from viewing your profile. They will not be notified. Comments on discussion boards from them will be hidden by default.
people are likely to comply (or say yes) to something if there is a reason given, even if the reason doesn’t make any sense. It’s the word “because” alone that triggers the automatic response of affirmation.
Always give a reason when you ask someone to do somerhing