Dogs attack Horses

I was riding my new horse back to base and when I got there I suffocated in a block for a second when I rode into a 2 block high space. I though nothing of it until I heard my dogs growling, so I let them roam around and realized they were trying to attack my horse. The only thing I could think of (since horses can't attack you) is that the suffocating in a block had triggered the dogs. I've already killed my dogs so I don't have a screenshot of them doing so, though.