日本人です

This debate is rolling on Twitter. Right-wingers argue that steal fortified mailboxes will teach mailbox smashers not to smash mailboxes. More lib/left users argue that the potential damage to the arm is disproportionate to the crime.

I think the answer here is pretty straightforward: ninja-armbreaker mailboxes are for when the rate of mailbox attacks is high (because the state isn't doing its job), and not for when mailbox attack rates are low.

The mailbox in question had been repeatedly vandalized, so the owner rebuilt the mailbox with an eight-inch pipe set three feet deep in concrete. An innocent party's vehicle departed the roadway, collided with the mailbox, and flipped. The vehicle's sole occupant was permanently paralyzed below the neck, and sued, saying that the proximate cause of his injury was not his loss of control of the vehicle and subsequent departure from the roadway, but the abnormally-strong mailbox.

Writing for the Court majority, Chief Justice Maureen O’Connor stated the Court has repeatedly ruled political subdivisions, landowners, and others owe a duty of care to drivers if they create hazards that “affect the safety of ordinary travel on the road.” Because Matthew and Diane Burr’s mailbox did not affect the safety of ordinary travel on the regularly traveled portion of Young Road, they are not responsible for the injuries suffered by Cletus Snay, she concluded.

By comparison, suppose that a man puts a landmine into his house. A firefighter could end up entering, and get blown up by the landmine. Life is full of unexpected outcomes.

Just like I won't put laxatives in my food to deter thieves.

Not sure how strongly enforced the rules are or if they're just guidelines or not, in the before times of 1986 when the movie Stand By Me came out there was a scene where "Mailbox Baseball" was being played and it inspired shenanigans which were made even more exciting because you could still ride in the bed of a pickup truck with no seats or seatbelts.

Homeowners got rightly fed up after a while and there were some broken arms and such as a result of that.

The mailbox is a target BECAUSE they assume the act will not result in any negative consequence TO THEMSELVES and as such think they SHOULD be allowed to cause damage with impunity.

And as a last thing? There is no comparison between putting up a reinforced mailbox to putting a mine in your house, because any given mine could kill any given person entering your house, firefighters being only one of many possible situations where you murder someone (or kill yourself) for taking the wrong step.

And the mailbox? Again, the comparison to a tree is far more apt, because the only way it becomes a hazard onto a random passerby is if a situation has already occured that puts them uncontrollably into it's path.

a mailbox is replaceable, human lives are not, and even a broken arm can be debilitating, especially if you’re in the US and the healthcare to treat it may be unaffordable

Nobody is having a gun put to their head and threatened into wrecking mailboxes. There is no situation in which someone is obligated to smash mailboxes. At no point does a person smashing mailboxes even gain any sort of benefit from it; it is an activity which is taken part in solely for the purposes of intentionally causing stress and/or financial harm to victims who have done nothing to deserve it. To say nothing of the fact that the reckless driving involved puts anyone on the sidewalk or the shoulder of the road at night in far more present and active danger than anything a reinforced mailbox can do.