It's an interesting question. I suspect most FEO's think blackpowder guns are nothing more than smoke-poles and not powerful enough to drop a deer at 100-200yards.

I have to admit that many years ago before I took up using muzzleloaders I had a similar opinion, that was until I saw one fired from the prone position. I was amazed how fast the bullet got to the target,(100 yards) and the recoil pushed the shooter back a few inches. As I learnt more and got bit by the bug I gained a healthy respect for the black art.
If the FEO's were more conversant with muzzleloaders and were aware that a trained marksman using a .577" Enfield could consistently put a bullet in a 4" square at 300 yards, (or was that 400 yards) they might think differently.

I suspect also that one of the problems with taking live game with a muzzleloaders is that they can be inconsistent. (I might have opened a can of worms here).
I knew someone who had a flintlock rifle. It took him 2 years to get the patch/powder/lube combination right. But, when he did, he could shoot cloverleaf patterns everytime, but how many of us can do that?

I think my .41" rifle would knock over a bunny at 100 yards and I would like to try if I could get it on my FAC for pest control.