AITA For refusing to walk our dog.

This was a while ago but I want to know if I was TA. I lived in my moms house until I was 20. When I was about 16 she floated the idea of getting a dog as a gift for my step dad, I immediately said that was a horrible Idea, dogs are a responsibility, they are not gifts, they are a family decision and should not be made impulsively, on top of that they wanted to get a big string purebred dog. I knew as soon as it grew it would be a problem because they won’t train it. I told all of this to my mom and I promised her that if she went ahead with it it would be their responsibility, not mine. I told her I would never walk the dog. I got outvoted Mom 50 y/o sister 13y/o and brother 7 y/o vs me 16y/o. Don’t get me wrong I love dogs, but that’s the same reason I would never get one, I am lazy and dogs deserve better. She went ahead and got the dog, everything was awesome when he was a puppy but then he got big, all of a sudden he was too strong for my brother and sister, so it was just my mom and step dad, and it started. “Im tired today” “my back hurts” “i sprained something” “can you do it tonight?” I held out for a good year, then I gave in and started walking the dog when they “couldn’t”. Here’s where I want to know if i was the AH. On the days when they made their excuses and I refused to walk the dog out of principle they would let the dog go in our very tiny yard, you could see this little heart breaking when you opened the door to the yard because he knows he wouldn’t go on the walk he was looking forward to. The dog doesn’t deserve that. I could’ve very easily walked him but I didn’t to prove a point so basically the innocent dog suffered so I could say “I told you so”.
AITAH?