What are your opinions about dressing your pet up?

Always been curious about this... I used to think it was awful that people put clothes on their little chihuahuas and carried them around like an accessory... HOWEVER... even though I believe that's stupid to do, I have seen people put sweaters on their pups for the colder months. This is understandable. I may do this for my pup when it gets colder out. Some animal rights advocates think it's wrong to dress your animals up whereas other people simply do not. What's your opinion about this?