So this is not new behavior on his part? The two of you have settled things like this before? Have you seen him do this with other romantic partners or friends?
If this is just W being W and you know you will go back to being friends again you could decide just to let him do his thing until he is done. Or whatever worked before.
If this not talking to you and bad mouthing you is new, or you have seen him do it to others, you may want to contemplate if he is the kind of person who pigeon holes people and now that you have been shifted to "not friend" slot there is not much to be done.
Leetah