Do you feel the same about physical security? It's fine for people to walk around your building, peak in the windows, maybe pick the lock on the door, maybe even take a little walk inside, as long as they don't steal anything?
What matters is if the thing they're doing to test your security is similar to what criminals would do to breach your security.
In the case of a physical location, that bar is low. It's things like seeing if your garage door is open, or your car doors are locked, etc.
In the case of computer resources, that bar is high. Probing your database for permissions holes is absolutely something that a normal "cyber criminal" would do. It's the equivalent of a carjacker looking to see if your doors are unlocked.
So an "online neighbor" alerting you that your database is unprotected doesn't feel weird at all. It's not the equivalent of that weird laser pointer thing you talked about, it's the equivalent of looking to see if your car doors are unlocked while you're away on vacation.
As someone else mentioned this would be more akin to a security officer of some sort waking me up and letting me know I left my front door open. I'd sure as hell be shaken but they were doing their job and I'd be thankful for that.
If i leave that filing cabinet in the middle of Times Square in Manhattan (which has an insane amount of foot traffic every day), then yes, I would expect plenty of people to give it a little wiggle to check if it’s locked. And I would be rightfully given a lot of questionable looks for complaining that passerbys stop to check it out or give it a wiggle.
Having your service on the internet is not the same as having a filing a cabinet in your house. I think that the Times Square analogy is even underplaying it, given that on the internet, your audience is many many magnitudes larger and more remote/anonymous.
On the other hand, if I had a private VLAN (that wasn’t exposed to the internet) on my home network, then I would be definitely annoyed if my houseguests would try and pentest it without asking.
If a neighbor came to me and said, "Hey, your mailbox that's located at the end of your long dirt driveway is protected by a wafer lock that can be opened by simply slapping the side of the mailbox in a funny way," I would maybe wonder why they were slapping my mailbox but I would be grateful that they told me and I would want them to continue doing whatever weird shit they were doing (so long as it wasn't causing damage).
When you put property in a public (or practically public) space, there's an expectation that it will not be treated as though it is on private property. There's a big difference between someone jiggling the door to your home (where you physically reside) and jiggling the lock on a mall gumball machine or the handle on a commercial fire exit.
There is a big difference between the digital world and the physical one. Many actions e.g stealing are very different in these 2 worlds and have very different implications.
The internet is like the former not the latter and taking a moral high ground stance that it just should be otherwise is just screaming underwater while doing nothing to actually protect yourself from an actual real threat.
I'd be very thankful if I moved to some place I'm unfamiliar with where people lockpicking is just a cultural norm and someone warned me I should get a better door.