If you have guns and kids (really, other people in general regardless of age) in the same house, you should teach them gun safety. What constitutes gun safety varies depending on the age, but most kids who can talk in complete sentences can learn the rules of gun safety. You should also keep your guns secure. Even the best kids are disobedient little whatsits at times.
There are two common formulations of the basic rules of gun safety. The NRA's three rules (with additional rules),
https://gunsafetyrules.nra.org/, and "the Four Rules of Gun Safety" that I believe are attributed to Lt. Col. Jeff Cooper,
https://www.hunter-ed.com/gun-safety/.
@123Chickadee: For the record, I'm not a big fan of Doylist interpretation because I think the text should make sense regardless of what the author is trying to do. I think this is why I've always hated Hollywood's moralizing but am fine with things like Aesop's fables. Aesop was competent at teaching a lesson in an obvious, but not clumsy, way. Hollywood fails more often than not.
@Morris: Harry does incur some moral obligations in being able to teach someone about magic before he even makes a decision. In this world, if he doesn't teach them anything, they are likely to try the "Jedi mind trick" and then it's too late. So, I think his minimal moral obligation is to say "these are the rules; if you break them, scary people
will come and kill you." If he does anymore than that, it gets complicated fast. Magic is dangerous. He first has to teach the student how to not accidentally cause harm. Then he has to teach them a bunch of other stuff, all the while teaching them either obedience or trust, preferably, both. That's where he failed with Kim. She was neither obedient nor trustful towards Harry. Magic is "serious business." When you're teaching "serious business" to someone, there needs to be a relationship of trust and obedience. That's why it's a master and apprentice relationship. And when that relationship doesn't exist, and both parties are adults, then the fault isn't necessarily on the teacher.
Harry basically says "this is dangerous, do not do it." Kim neither trusted nor obeyed. We don't know enough about their relationship to say who has what proportion of blame, but Kim did come to him. That alone is an admission that Harry knows more than her. But this isn't a failure of withholding information. It's a failure of giving too much information before establishing the ground rules, if anything.
To get back to the guns analogy, it's kind of like teaching you the gun safety rules, the mechanics of shooting, and stopping at that. Just about no one seems capable of keeping the muzzle pointed in a safe direction at first on a range. I have to stay on top of them and watch everything they do. Providing information isn't enough. Maybe providing more information would have worked for Kim, but Harry shouldn't have given her anymore information. It's a
summoning circle. If it's primary purpose was binding things already here, it would be called a
binding circle. As she is clearly lying about her intentions, Harry shouldn't help her because she's probably trying to summon some terrible being. He should probably have contacted Morgan about it, but obviously never would have because of Morgan's behavior (an example of bad police work, there).