I must be misusing the word fair, I'm not familiar with the usage you're hinting at.
I'm not trying to anthropomorphise but it's a reasonable extrapolation that they experience their own lives (certainly we have no real understanding of consciousness to apply to measure and prove or disprove this yet, but we cannot wait for it). With that assumption the life of (for example) a cow as livestock can be seen as a significantly worse experience for the animal than their natural/wild lives would have been, although still not optimal since they are subject to predators and other bad things. To not accept this as unkind or "unfair" treatment seems to be based on the assumption that they are really unconscious automatons that regulate some meat hanging off them - essentially a algorithmic restatement of the "they don't have souls" view from the past.
Link: boingboing.net/2011/06/30/richard-dawkins-on-v.html
Imagine a being so vast and powerful that its theory of mind of other entities would itself be a sentient entity. If this entity came across human beings, it might model those people at a level of resolution that every imagination it has of them would itself be conscious.
Just like we do not grant rights to our thoughts, or the bacteria that make up a big part of our body, such an entity might be unable to grant existential rights to its thought processes. Even if they are of an extent that when coming across a human being the mere perception of it would incorporate a human-level simulation.
But even for us humans it might not be possible to account for every being in our ethical conduct. It might not work to grant everything the rights that it does deserve. Nevertheless, the answer can not be to abandon morality altogether. If only for the reason that human nature won't permit this. It is part of our preferences to be compassionate.
— Albert Einstein
How do we solve this dilemma? Right now it's relatively easy to handle. There are humans and then there is everything else. But even today — without uplifted animals, artificial intelligence, human-level simulations, cyborgs, chimeras and posthuman beings — it is increasingly hard to draw the line. For that science is advancing rapidly, allowing us to keep alive people with severe brain injury or save a premature fetus whose mother is already dead. Then there are the mentally disabled and other humans who are not neurotypical. We are also increasingly becoming aware that many non-human beings on this planet are far more intelligent and cognizant than expected.
And remember, as will be the case in future, it has already been the case in our not too distant past. There was a time when three different human species lived at the same time on the same planet. Three intelligent species of the homo genus, yet very different. Only 22,000 years ago we, H. sapiens, have been sharing this oasis of life with Homo floresiensis and Homo neanderthalensis.
How would we handle such a situation at the present-day? At a time when we still haven't learnt to live together in peace. At a time when we are still killing even our own genus. Most of us are not even ready to become vegetarian in the face of global warming, although livestock farming amounts to 18% of the planet’s greenhouse gas emissions.
So where do we draw the line?