Long before I knew anything of ballistics, bullet weight, foot/pounds of energy or any of that disiderata, I was taught how to hunt, how to shoot and took several deer with a
Model 92 rifle in 44-40 and factory loads. I know that the 30-30, 32 Special and 38-55 are all quite adequate and will take deer reliably, not to mention moose and black bear.
Over the last nearly half-century I have taken deer with the 44-40, 44 Magnum, 30-30, 348, 308, 270, 45-70, 30-06, 35 Whelen, 25-06, 257, 264 WM and even one with a 450 Alaskan. For the last 9 years I've stuck with the 257, but wouldn't hesitate with a 38-55 and some good lead handloads.
Ethics have a lot more to do with what, where, when, why and how you hunt, your conduct (especially when you think no one's watching or will know) ... than with what cartridge you may choose to use. Sure, "use enough gun" as they say, but you don't have to necessarily go overboard either. I'm fairly certain that the deer today are no tougher than they were at the end of the 1800's.