They have a strong emotional bond while the calf is dependent, probably through the calf's 1st fall. Beyond that, unsure. Because of that, I passed on the last 2 cow/calf pairs I found while carrying cow tags.
It doesn't matter what other guys think, you and I have to answer to ourselves on moral matters.
Having said all that, I recall reading a biologist's opinion some years ago that shooting a calf has less impact on the herd than shooting a mature cow. His reasoning: calf mortality is built in to elk evolution. Odds are 50/50ish the calf is male. Adults are more likely to survive any winter than calves of the year. And a cow w a calf is a proven successful breeder, while a female calf may not be. The one elk most responsible for herd survival is the lead cow, usually one of the most experienced (oldest). Probably best not to shoot her, for herd and meat quality reasons.
IMO, the best antlerless elk to take is a yearling cow.