Guess there are no houses with windows in them? Or mushboard sheathing? Vinyl siding? No 1/2 inch drywall? No unfinished rooms?
The point was, you are legally responsible for every round leaving the muzzle of your weapon and that should be just as much a consideration as if home invaders might be wearing body armor, if not more.
I apologize, I thought you were saying 5.45 rounds were going to over-penetrate through walls.
I agree completely. My biggest concern is collateral damage. That's why my primary home-defense weapon is my AR-15 loaded with 50 gr. V-Max .223 rounds. I like those rounds because they're extremely effective and yet they're less likely to over-penetrate.
And you're completely right about being responsible for every shot; if someone uses a rifle for home defense and ends up firing more errant shots because it has a high capacity and is easy to shoot fast, that defeats the purpose of having a weapon that under-penetrates walls.