Knowledgeable guides aren't bashing any specific "caliber" (meaning cartridge) but the hunters who typically can't shoot a new-to-them, hard-kicking "caliber" accurately. Which is exactly what Phil was doing, and my outfitter acquaintance in the Bob Marshall.
They're also bashing the claims from many "magnum" fans that only a certain minimum, magic level of caliber/velocity/energy/bullet-weight is adequate (or sometimes "fully adequate") for certain big game animals. This is often what convinces some newbie elk or brown bear hunter who already owns and has hunted plenty with, say, a .30-06, that they MUST use a far more powerful cartridge, or the elk or bear won't die.
I know part of this due to having guided some myself here in Montana. Quite a few hunters on their first pronghorn or mule deer hunt decided they needed some sort of belted magnum, usually a 7mm or .30 caliber, to kill pronghorns and mule deer at "long range." Long range to many of my guidees was anything beyond 200-250 yards--as far as they'd shot anything back home.
So they bought a new magnum despite owning a very familiar .243 or .270 or .308 Winchester they'd already killed a pile of whitetails with. Often they wouldn't shoot the new MAGNUM enough before going on the hunt, because it kicked too much or the ammo was expensive. As a result they flinched enough to be unable to zero the rifle adequately.
This may seem impossible to many manly magnum fans, but have seen it many times, both while guiding and when hunting big game in various places around the world. One was a guy who brought a new 7mm Remington Magnum on a pronghorn hunt, leaving a .243 he'd killed plenty of whitetails with back home. Another was a European guy who'd hunted Stone sheep and caribou successfully with his 7x64 Mauser in British Columbia, killing both with one shot--but when he decided to hunt moose with the same outfitter a couple years later bought a .300 Winchester Magnum, because moose were so much bigger. He grouped three shots in about 18" at 100 yards during the pre-hunt sight-in in camp, and not only took several shots to kill a moose, but several to kill another caribou.
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.” John Steinbeck
