I dont think so. Why would morality inhibit progress. Stale knowledge does prevent, but morals dont really change. By morals being flexible, I mean - “Killing is very bad, except in so and so situations, you have to”.
You assume that what’s considered “moral” or ethical hasn’t changed multiple times throughout history and that it isn’t subjective. Sorry to sound pedantic, but once again, it’s right in the definition of the word:
a person’s standards of behavior or beliefs concerning what is and is not acceptable for them to do.
And nowhere does it say that “morals” imply any degree of immutability. There are countless examples I could make. Just as a personal example, I never particularly paid mind to the suffering of animals until I adopted a pet. I never believed getting involved in political discourse was a duty until I realized how increasingly distorted it’s becoming. Many people say similar things about having children, how the experience just changes the way you see the world, your perception of what is tolerable and what is not, and ultimately your perception of “right” and “wrong”: your morals.
If we as humans didn’t believe that we can actually influence other people’s conceptions of what’s right or wrong, there would be no point to education, history, politics, philosophy, law, religion, art, literature… culture as a whole. We wouldn’t have communication or civilization.
My honest opinion is that what you’re truly asking here isn’t whether it’s okay/possible for morals to be flexible, you’re asking whether it’s okay to stray from what you’ve always perceived to be the general consensus of what is “moral” and what isn’t. And my answer is still yes.
You are not going to find a clear definitive answer to that question, for the reasons I’ve explained. If we as a species had a single, universal, correct answer to that question, a solution that somehow fairly handles all the infinite variables of context, cause, effect and emotion, according to a supreme, universally pleasing standard of justice, we would be living in a utopia. Or in Heaven. We wouldn’t be here having this conversation, and we wouldn’t be constantly teasing ourselves with debates or thought exercises like “would you kill Hitler if you could?”
YOU need to pick that answer for yourself. You have to come up with the best solution that you feel comfortable with after taking in consideration the variables of context, cause, effect and emotion to the best of your ability and knowledge for EACH experience you have. Then you’ll have your “morals”, and those are the only ones you should follow.
And yes, like I said before, this is complex, and scary, and difficult and absolutely exhausting. Which is exactly the reason why some people turn to religion or anything that promises the illusion of a ready, stable, immutable answer in a world that is constantly changing and constantly requires them to re-evaluate everything they know.