Removing the sling for field use was standard operating procedure in the Infantry. Still is for some. But, yes, it's a pain to deal with dragging out a deer. Nonetheless, the deer can and should get a piece of that.
What's really being said is there are better ways to hump all that gear when dragging out the deer, and that goes to a slick poly sheet tied to it (a kids snow toy,) or even a wheeled hand cart. Yes, I've even seen a father son team pushing a squeaky wheelbarrow. Drag enough deer out on their bare hide and you'd almost give your gun for a wheel. Right now, I'm leaning toward the golf bag cart. Lightweight, strong enough, and dirt cheap at DAV, Goodwill, or the Salvation Army store. They fold down, if you hunt a stand, you can pack it in.
You can rig up any sort of wire or loop to fasten the front of the sling, either milspec wire bits, clamp mounts, or paracord. Slings are a convenient way to carry a rifle not being used, but for rapid off hand shooting, in a tree stand, or in a blind, not so much. Practice on a moving target or popup range with one before claiming the Sling of the Month is exactly what a CQB instructor recommends for casual hunting. They have their drawbacks. If the mount is connected to the barrel, expect a POI shift. Body slings are snagged constantly moving cross country in thick brush, and actually restrict movement to one side when the other shoulder just might be needed - or a tree trunk is in close proximity.
Sling, not so much, just a simple strap to use walking out for the last hour - and that's still not optimum, it's good hunting then. Better at the ready.
Have you tried dragging a deer a mile while carrying a rifle in your hands? 
