Not to quibble but this is just not true. I've assembled and disassembled both top to bottom. My personal ARs were all built by me. The only difference in design is a drillhole and a sear.
IMO - the "oh it looks scary but it's not" argument is a fail legally and on principal. We're allowed, by law, to have both, and both are deadly... as intended.
Most shooters are actually *more deadly without select-fire. Almost zero mil or leo use full-auto 5.56, for good reason.
See Post #24