Safety is actually one of the key tenets mentioned in the LOTG. From page 12 upfront in the 2018/2019 LOTG:
Although accidents occur, the Laws should make the game as safe as possible. This requires players to show respect for their opponents and referees should create a safe environment by dealing strongly with those whose play is too aggressive and dangerous. The Laws embody the unacceptability of unsafe play in their disciplinary phrases, e.g. ‘reckless challenge’ (caution = yellow card/ YC) and ‘endangering the safety of an opponent’ or ‘using excessive force’ (sending-off = red card/RC).
Rejoinder: 1) was talking about the careless standard (e.g., a foul exists v it does not exist), 2) historically the divergence in the standard relates to the divergence with rugby, not their desire to make the nascent game more safe (besides 19th century sports were much more dangerous in most comparison to their modern counterparts, which is surprising given how medical knowledge wasn't as advanced...our ancestors were made from sturdier/more reckless stuff [depending on your point of view]), 3) this parts just IMHO but I think the stuff about safety is largely lip service at least as far as the current rules go...if safety really was a priority they really would do something about the heading (not saying they should, just that if it was the main priority they would), and 4) the rest of your post seems to support my proposition in 3.
BTW, I agree that refs in socal are too slow and unwilling generally to show cards.