You aren't an evil dog owner. However, your mother may be concerned since she has a Boston Terrier. This breed has very thin coats and the cold can affect them. You have hairy dogs. Ask yourself if your dogs are shivering and trembling when they go out. If they aren't, don't worry about it--they are warm enough. I honestly do not like clothes on a dog--bandannas can be cute however.

I have several jackets that my current dog inherited from my two previous dogs. She hates them and I will only put one on if it is bitter cold. She is a Scottie and I will say she would really look cute in a red tartan plaid jacket, but it is a no-go. When one of my previous dogs was ill, she required monthly ultrasounds and was shaved. She would shake in the cold and I did put jackets on her for her comfort. She even had a little poncho that she wore in the house on really cold days. Of course you know you are obligated now to post a photo of the lovely shih tzus.