The acceptance of slavery was not universal. Back then there were already people, abolitionists, striving to end slavery. So looking at what small but vocal groups protest now can give a hint at what future people could find wrong or evil.
It's not at all arrogant to think future people will share my ethics, just like abolitionists were not arrogant to hope for a world without slavery. Arrogance would be believing they'd share all of your ethics, and just as well I'm sure most abolitionists were still very racist, sexist, homophobic, ...
Ethic shifts don't come out of the blue; they start as a growing sentiment within a population, which at some point (whether through growth or things being shaken up by e.g. war) reaches critical mass.
>Sure but that's no reason to expect yourself in specific to be on the right side of the shift.
Everyone from Caesar to the crusaders to Martin Luther to the American revolutionaries to the KKK to the Amish to the imperial Japanese to the 1960s hippies to the Taliban to the IRA is on the right side of the shift as they see/saw it.
We can't all be right, some people have to be wrong. Some people will be right on some things and wrong on others. Some people will be so right or wrong on particular things that it will overshadow how right/wrong they were on others.
Clean in vitro meat might be the technology that ends factory farming. An interesting question is how future generations will look at us if they still eat clean meat.
Describing lab-created genetically-modified "Frankenmeat" as "clean" might be one of those things not looked on favorably in the future... Bill Joy is quite likely right that genetic engineering is probably the most dangerous technology ever created, and the one that almost certainly has the highest probability of killing us all.
It may be the most dangerous of technologies currently on the horizons, but it can also have the biggest payoff - it's not just about things like curing diseases, test tube babies, or selective pathogens - it's also the first stop on the way to building living machines, living materials, and cracking molecular nanotechnology, which life is nothing but.
Compared to factory farmed meat it is most certaly clean. No unnecessary suffering of concious animals and far smaller impact on the environment make it that.
I'm not even sure that clean meat relies on genetic modifications, but even if, so what? There is no reason to believe that targeted changes are more harmfull than random mutations.
The point of the exercise is humility — to think about how people in the future might think your ethics are wrong and evil — not arrogance.