My mother in law is so bizarre. She always supports my husband even when it's obvious he's wrong and it makes me feel like the outsider in the family. It's very very frustrating and humiliating. What can I do?

I suggest, stay out of it. Perhaps, she does just to annoy you. She knows that you get irritated by it and she wants just that. Next time, if it happens, just leave the room or the discussion. If she will come to know that you are unaffected by her behaviour, she will stop doing that. And even if she doesn't stop, atlas you will have peace of mind by not listening to what goes on between the two. They are mother and son, let them deal their nonsense, why you take the burden! Leave your husband and mother-in-law for good for a while. Your husband, too, will feel your absence and when he does, then tell him what you feel and how wrong decisions can hamper both of your lives.