You can down load any caliber. But to say my so in so can shoot this. Without specifying that you are down loading and they are shooting mouse fart loads. Is just implying that the person is a "pussy" as that is what comments like that comes off as...
I think it might be worth mentioning that, while almost any cartridge can indeed be downloaded into a "mouse fart" by a competent handloader, the .45-70 is one of relatively few cartridges that can be purchased over the counter in a wide variety of power levels. If a new owner is not yet into reloading...or perhaps never will be...he can buy one of the Trapdoor-level factory loads that is safe in any rifle and is very tame and sedate. If he wants to do battle with dinosaurs...he can buy that type of load right off the shelf as well.
And, honestly, I think that the intervening years just might have helped turn the memory of an ouchie on the shoulder into the "memory" of being pushed back three feet by a rifle shot. To be pushed back three feet would indicate that your leading foot took a step back...and then your other foot also took a step back...and then likely your leading food took another step back. Did that really happen?
A typical .45-70 hunting load will produce much less felt recoil than a typical 12-gauge hunting load. Guys shoot a box or more of 12-gauge hunting loads in a morning of standing in a duck or goose blind, and don't seem to be crippled by it...but then they shoot a couple of rounds through a rifle off the bench and reach for the Advil, even though the recoil energy is less. Shooting position matters; stock fit matters; and most importantly, mental outlook matters.
Recoil is largely in the mind. If you "know" it's gonna hurt...you're right, it will. Too many "know" it only because they were told by someone else. Did the OP come up with the idea that a .45-70 would "just blow a deer to pieces" completely out of his imagination? Did he decide that it "may knock me on my arse" all on his own? Nope; he just read too many horror stories from other people, who read too many from others still.