They aren't forcing you to buy Freddy, only to have the character on your console so that people that DID buy him can use him online.
If you are fighting against someone when you dind't download Freddy, then the other person won't be able to use Freddy. Right now they are making sure that you can use Freddy online every time instead of relying on the people you play online.
Again, you don't have to pay anything. Only download him, you won't be able to use him till you buy him though.