I’ll go first.
As strange as it may sound, I think the thing they will be most shocked by is that we allow hunting and that we kill animals to eat them. Yes, I’m serious. As populations become increasingly urban/suburban, they’ve lost touch with animals as anything but pets. We see the results of this already as people are demanding better treatment (human-like treatment actually) for farm animals and the elimination of “inhumane” hunting practices.
It strikes me that the natural progression of this will be a slow but steady push toward vegetarianism, especially once science finds a way to duplicate the taste of meat (not like those awful veggie burgers, but real meat). At that point, I think you will see people conclude that killing animals is wrong, and they will eventually look down on us for all those tasty, tasty, tasty steaks we eat.
I think they will also look down on us for racism (by all races), religious intolerance (mainly Muslims, but also Christian fundamentalism), and for being anti-science (both things like opposing gene therapy and things elevating junk science, e.g. climate change, to a religion). This last one will be seen as superstitious.
Thoughts? How do we look in hindsight to you?