Let me ask you this - would you want to get hit by an AR 15 in the chest at 300 yards?
NO! Of course you wouldn't!
Now, consider this.
If you fire the EXACT SAME .224 55gr projectile, and it hits you at 100 yards from a P90, or 50 yards from an FN FiveSeven, in the same place, it will do the exact same thing to your insides. Once that projectile leaves the weapon it doesn't matter WHAT weapon fired it, or what chunk of brass it was expelled from.
The same terminal effects can't be said of a soft lead 22 rimfire.
Why doubt the experts? Let's just all run around the internet, parroting whatever they say, and accept it all as gospel. By that logic we should throw all of our guns in the furnace, because there's been a lot of irrefutable evidence that suggest that guns kill a lot of innocent people.
The 5.56 NATO cartridge has a universally accepted maximum point effective range of 550 meters, with consistent yaw at 300 meters sufficient to cause fragmenting of a standard M855 projectile. It's been in service for over 50 years and has sent a lot of enemy armed combatants off to the great beyond.
I'll repeat my previous statement - the same, exact projectile, fired from a P90/PS90, has the same energy at 100 yards as an AR-15 has at 300 yards. The FN Five Seven matches pace at 50 yards. There is more than enough energy, at those ranges, to get the job done.
We, as civilians, can purchase and use projectiles which are highly volatile. The initial 5.56 NATO cartridge - the M193 ball round, was considered to be inhumane because the tissue damage was so severe. So they went with the SS109 M855.
Quoting the same source used on the Wikipedia article:
"International Legal Initiatives to Restrict Military Small Arms Ammunition W. Hays Parks∗ Copyright 2010 by W. Hays Parks International Committee of the Red Cross (ICRC) page 1–18" (Which list International Committee of the Red Cross, Austria, Argentina, Belgium, Bolivia, Bulgaria, Burundi, Cambodia, Cyprus, Germany, Ireland, Latvia, Lithuania, Luxembourg, Mauritius, Mexico, Romania, Samoa, Slovenia, Sweden, Switzerland, etc. as parties that consider the 55 gr M193 round to be inhumane) "
In addition to the M193 ball ammunition, civilian shooters have HUNDREDS of projectile types which they can load in to a 5.7x28mm casing. Any .224 projectile 55gr or under makes a suitable candidate. Many of those are light-skinned, highly-frangible hollowpoint projectiles which essentially detonate on impact with soft tissue. 100% of the kinetic energy is transferred to the target, and each fragment creates it's own unique wound channel through the target.
Your chances of cutting major blood vessels and disrupting central nervous system function are massively increased with multiple crushed impact tracts.
Your venerable doctor (he's talking about the dentist) makes the assumption that projectiles remain INTACT after impact - and this point is very clear in his research where he posts cross sectional comparisons of an INTACT sidelong .224 40 grain FMJBT projectile next to a 9mm which has mushroomed out.
Every single one of the 5.7x28 .224 grain projectile I have ever managed to recover has been fragmented. These projectiles - quite literally - detonate when they impact soft targets. The crush zones for tissue destruction are amplified in a cone shape interior of a couple inches from point of impact as the projectile passes through the target. They do NOT make one wound channel as 9mm/45ACP/etc will create. They make MULTIPLE wound channels as they traverse the target, each one of those channels capable of inflicting arterial or nerve damage.
In addition to permanent crush cavity, supersonic temporary cavitation cavity, and multiple wound channels, there is significant laceration capability as the jacket and core are separated and mangled upon impact. This laceration capability, while not of primary benefit to direct incapacitation, will serve to sever more muscle tissue and blood vessels than an intact projectile will.