I agree. There's no reason a Friend Invite that we haven't accepted should block us from being able to Blacklist someone. SE should fix this so it doesn't get exploited any more.

There was one point of the OP I did find a little odd, though. It was this bit:

Quote Originally Posted by Braanu11 View Post
I had to go into my Friend's List, decline the friend request, and ...
Why would you take the extra step of opening your Friend's List? If they've sent a Friend Invite, it should be right there on your screen already. You can decline it from there quicker than opening your Friend's List and finding them just to do the same thing.