WARNING: The following contains spoilers for Batman: The Detective #1 by Tom Taylor, Andy Kubert, Brad Anderson & Clem Robins, on sale now
Batman has come up against almost every kind of criminal and threat during his storied career as a crime-fighting and superhero. He's fought everything from reluctant avengers to devious murderers, with an unshakable code at the heart of his mission. But it turns out there's one kind of criminal that he has no illusions of restraint for.
While coming up against a band of terrorists who attack an ally within a hospital in Batman: The Detective #1, Batman reveals that people who target hospitals are the kind of criminals he has no mercy for.
Despite his usual commitment to fighting criminals primarily in Gotham City, Batman has to fly to Britain to find out more about a terrorist attack that specifically referenced people who'd been saved by the Dark Knight over the years. In part, he does so to help Beryl Hutchinson, the current Knight -- who was seriously injured trying to save lives during the attack. After visiting Beryl in the hospital to learn more about the attack and to check up on his longtime ally, Batman's monitoring tech is able to locate a handful of hostiles moving towards the building in an effort to complete their earlier actions and actually kill Beryl and her new sidekick, the latest Squire.
Confronting the group of killers who breach the hospital, Batman thinks to himself about how both of his fathers were "medical men" -- referencing Thomas Wayne's status as a doctor and Alfred's combat-time role as an Air Force medic. As a result, Batman notes to himself that he has no mercy for anyone who would attack a hospital. Instead of fighting them with any sense of restraint, Batman attacks with a brutal sense of efficiency, taking down all four attackers and tackling them out a window. He even uses his enemies to cushion his landing. He strikes as hard as he can against the killers, pummeling them with a brutal edge that "takes the fight out of them." Despite being outnumbered, Batman is able to force the four of them into a full and panicked retreat -- even capturing one of them to interrogate.
It's a minor moment for Batman, but a perfect hint at the kind of things that truly get under Batman's skin. While he may dedicate himself to fighting crime, he's also committed to saving as many lives as he can. Protecting people and ensuring no families go through the kind of pains he's suffered is a chief motivation for Batman. So seeing a group of killers who aren't only willing to take the lives he's previously saved but is capable of attacking a hospital -- another institution dedicated to saving lives -- truly enrages him. Their attack could have easily resulted in civilian casualties, and the fact they would even consider a hospital as an acceptable battleground flies in the face of everything Batman is meant to do -- find criminals and threats where they lurk, and keep places like hospitals safe.
With Alfred's death during "City of Bane" still hanging over Bruce, it could be seen as a very raw nerve for his newfound enemies to messing with. Especially considering how many times Bruce survived his mission as Batman only thanks to the intervention of Alfred and his medical skills, it speaks to how seriously Bruce takes that practice -- and how much it genuinely offends him that others wouldn't share that reverence. The fact that they do so in silver suits, designed to look like Batman, makes it only worse. It's the perfect thing to get under the Dark Knight's skin and the sort of thing that can leave an entire squadron of trained killers running in fear from a furious Caped Crusader.