The bit about the so-called NRA instructor who had his students practice a few rounds without hearing protection, so they could know what it was like if they got into a gun fight, made me think of other things people might want to practice (or have their more gullible students practice):
1) Have somebody kick you really, really hard in the crotch, because that is a fairly likely technique to be employed against one in a physical altercation;
2) Have somebody poke you in an eye (or both eyes, if you really want to go for hardcore training) with their thumbs, so you know what that's like;
3) Cut yourself across both hands and forearms, so you know what defensive wounds feel like;
4) You get the idea.
Deliberately doing things that are likely to cause injury, or even somewhat likely to cause injury, in order to "prepare" for what is already a fairly unlikely contingency is, how to put this gently, not smart.