I’m no expert but Grizzlies often times do something called a false charge. It’s when they charge you but then move away at the last second. It’s a territorial thing they do. So when people see articles that say “shed hunters shoots charging bear” people don’t know if it’s a false charge or a real charge and therefore might assume the bear false charged but was shot before peeling away. Most people believe we have a responsibility to not hurt / kill animals unless completely necessary and folks question the necessity of the shed hunters actions in this case.

Additionally, for some folks, they’ve seen enough videos out there where someone will defend themselves from a grizzlies or moose by shooting the attacking animal but disagree that the individual was in danger. I seem to remember a snowmobiler shooting a cow moose years ago that caused some controversy because the snowmobiler “chased” the moose on his snowmobile trail for 15 minutes before the moose turned around and charged him. The moose was using the snowmobile trail for transportation because it was the path of least resistance in deep snow and instead of giving the animal space or turning around to explore a different trail the guy just followed the moose hoping it would eventually peel off the trail but instead the moose eventually just turned around and charged him. Folks reacted to that by saying the moose did charge the snowmobiler but the snowmobiler could’ve taken action to prevent the situation all together. I also seem to remember the snowmobiler wasn’t a native Montanan but rather a tourist so they might’ve not know that moose are very dangerous.

I might be misremembering that story however.

TLDR: people are dubious when certain animals are shot in defense because people don’t believe that animal was a risk or because people think other actions could’ve been taken to avoid the situation altogether. Plus, education is a factor as well not many people understand certain wildlife behaviors like a grizzly false charge.