Less than 100 years ago making animals fight to the death for people's amusement was considered normal. Working employees to death in Sweatshop conditions was considered acceptable only shortly before that. And it was less than 50 years ago that we finally accepted as a culture that discriminating against black people both violently and nonviolently was no longer accessible.
Though honestly we're still working on that last one.
we like to imagine that morality is a simple logical process. But by and large morality is shaped by culture, until such time as peoples morality exceeds cultural norms.
And that's when you get into shit like what we have now where there are those who argue on a moral level that the mistreatment of one group of people or another is unacceptable while there is another group of people who argue on a cultural or traditional level that's such mistreatment is not only acceptable but appropriate. Or that limiting such mistreatment in fact harms them by removing their Liberty to mistreat others.
And the cycle will continue into Infinity. No matter how Progressive you are today 100 years from now or two hundred years from now you will be thought of as regressive in some manner or another. Culture continues to change. Morality continues to change.