Was I bashing his Mother?

No matter what, my husband claims I am bashing his Mother. If I say anything good, or mildly rude about her he jumps my **** and goes ballistic and screams that I am bashing his mother. He defends her no matter what she does and says she is perfect and has done nothing wrong. She got him a pair of jeans for Christmas and got the wrong size. I found them and said I will take them to get exchanged so that he will have the right size. I said "That's ok, your wife knows what you need and like". He went ballistic. I want to know wtf I did wrong.