So, we've also been using other animals for thousands of years, plus being racist towards other humans for thousands of years. Just because they're domestic animals, does that mean that they're different to dogs, in terms of their ability to suffer? Let's put this in the human context: would you justify racism and unequal treatment of humans by saying "these humans are should be given rights and be treated a particular way, in a fair way, and these shouldn't"? Just a thought.