
I had the exact experience a couple of days ago. Watching the anime as a kid, idk if the themes were just washed down or if I didn't understand the depth of it all but I loved Roy and all those characters in the military. As an adult, seeing them commit genocide and following through with their orders makes me sick to my stomach. Idek how this manga manages to redeem them, all except Armstrong who ran away actively engaged in genocide. And Armstrong still was shamed in the manga for abandoning his post when he didn't want to kill the elderly and women and kids. Roy just roasted them alive. And he's made out to be this new leader figure. I still can't wrap my head around it

Yes especially when Armstrong’s sister shamed him for leaving even though she knew what they were doing in order to make the philosopher’s stone. I think the main theme of equivalent exchange is represented when mustang goes blind in the anime, a bit of mercy shown by truth. Though what they did could never be forgiven and that is something they must atone every day for. I think the genocide may have been treated a bit too lightly at times in the anime, but I give it a bit of grace. Also when ed said that thing of “just because your people were killed doesn’t give you the right to kill others” when he first learned about scar’s past, I think that shows that even though he is a very intelligent individual he still doesn’t know a lot about how the world works or how it would feel like if that happened to you and I don’t mean that in a patronizing way or a mean way at all.

I definitely agree that mustang really has no ability to emphasize with scar. We all know with his personality and weaknesses he would've committed mass murders just as scar had done, had mustang been in his seat. But for mustang to outright state the cold logic of "killing is bad no matter what had been done to you" as someone who literally committed those atrocities against scar? He's entirely unsympathetic towards anyone of that ethnicity/situation. He always chose the weak way out; he could've abandoned post like Armstrong, he could've defected to help the other side in this one sided "war", but he didn't. Hard to see his character in the same light as an adult with full understanding of the weight of the themes.
reading the manga for the first time and it feels weird. I've watched the anime long time ago and I don't remember alot from it except thinking that's one of the greatest anime out there. but now idk. the genocide stuff are rubbing me the wrong way. Roy and the rest are also rubbing me the wrong way. I'm just on chapter 10. I'll keep on reading. maybe the story will hold it's weight and will stop being icky(?). insay icky cuz idk how to describe how I feel about it.
it really is an interesting timing to start this.