Is it possible to decline all friend requests?
Solution 1:
The only way is to max your friends list out so you can't get more requests. The max is 100. So get 100 friends on there and just delete one when you want to add one. Wish there was another way as it's annoying.
The only other way is to get a WoW account and use the addon BadBoy to auto decline them all while in WoW.
source: http://www.reddit.com/r/Diablo/comments/1ugcbg/anyone_know_how_to_stop_the_spam_of_pvpbank/