A. There are several ways to show something as munitions grade lead that I can think of off the top of my head:
1. You analyze the orientation of the material to indicate it was refined and smelted, not naturally formed. (which would appear as haphazard and impure)
2. You identify the exact mixture of lead to other alloys which may go so far as identifying the bullet manufacturer.

B. Something need not be illegal to be immoral. Laws set minimum standards for human behavior, not ideal behaviors. Someone that rests their laurels on the notion of being "a law abiding citizen" is no man of measure. Frankly, a man is judged by being on the right side of history regardless of whether they are in compliance with the law or not. E.G. how many people (Charleton Heston included) violated civil ordinances to march with Dr. King?
1. In the case of the probable wholesale slaughter of the prairie dog towns I was speaking of in the Red Desert of Wyoming, you're missing the point.

What do you call it when someone loads up piles of guns, drives or flys hundreds of miles to public BLM land where they have NO stake in protecting crops, ranches, cattle or horses, and they decide to destroy every animal of a native species as they can for recreation? What would you call the person if they choose to use frangible ammunition that creates a explosive effect where the prairie dogs have an even more awe-inspiring death than when hit by FMJ bullets?

You call that a sportsman. I call that a sociopath.

Someone is traveling to a location with no intention of harvest, no intention of use, no intention of protecting habitat supported by science, no intention of protecting agriculture lands, no motive other than to observe animals dying for their own pleasure.

That is the same mindset of a child that would enjoy hitting kittens over the head with a baseball bat. It isn't purely the action, it is the motive behind the action. The motive in the case above is personal pleasure and it is not offset by a guiding principle or benefit.

We create hunting laws that establish protections for people from being charged with animal cruelty laws. The argument in law is that the results (death or injury) to the animal aren't what should be judged, but rather the intention of the participant. It is the motives that determines whether someone is evil or good, immoral or moral. Using the shield of hunter's protections to pile up wildlife to rot and kill other wildlife without any just motivation, harvest, sustenance or protection of one's property is just not hunting. It's sociopathic behavior being cloaked under the veil of "hunting" and it doesn't need to be supported, it needs to be excommunicated from within the sporting community.

Also: Raptors do not eat grit and gravel nor do they have a "gizzard" as you put it. They do not defecate pieces of lead ingested either, at least not if they have any size to them whatsoever.

I'd like to point out this all started with a polite suggestion from a fellow hunter to just "not be part of the problem" resulting in a lead ban. Clean up your field of carcasses or dig a pit and bury your gut piles and everyone can enjoy their liberties indefinitely. The response was "you're full of crap", "I disagree completely" and "you're not a real hunter, you're a gun grabber". At the end of the day, whether the science is true or false, the bans will happen because people are unwilling take simple steps to clean up which will send the message hunters cannot be trusted to self regulate.