We are coming up on our 25th wedding anniversary in June (the same day our 8th baby is due!). One thing I have learned, mostly the hard way, is to let things go.
You know this is a failing and weakness your husband has, just like you have failings and weaknesses of your own. I'm not saying it is right or good, just that "love covers a multitude of sins".
Let it go.
You know it was a joint decision to sell the dog and so does he. His saying it was YOUR fault doesn't make it so.
I preach this to my children every day. You don't have to respond when someone is being contrary. You don't have to correct them, set them straight, or teach them a lesson.
Let it go.