I had a bit of a think about this. We have an input field, something that invites anything that one might type into it. The input field might constrain what is typed in and the programme behind it might decide to believe the content or not.
Does the input field make it clear that it considers some sorts of input as invalid? I can't recall seeing any login related field that specified its input requirements - that is sometimes part of the "security"(through obscurity) of such things.
IT related security as it relates to logins might be unfairly compared to a front door and keys and other physical security devices. However, few of us have access to enough steel and concrete and other fancy materials for physical security to make this comparison stand. We do have access to wealth of IT security which is freely available. It is bloody complicated but freely available. You do need to be able to sift the good advice from the bad but it is available.
The final bit of the puzzle revolves around responsible disclosure. This is not something you see in the world of safes and front doors. It is an established industry practice in IT, in an industry that is very, very young but one which moves very, very quickly.
Even if the login fields specify that unauth. access is naughty I would argue that given that the tools are freely available and that any reasonably competent developer should be able to sanitise input, then you can't complain if someone types in complete crap.
IT is still discovering Engineering but it has so many more resources for instruction and guidance than bridge builders and boiler makers had in the early days and it moves so fast. Do you have any idea how dangerous steam trains were in the early days? Steam is a bloody powerful thing under pressure. Do you have any idea about resonance and concrete cancer? IT is still having its Tacoma Narrows and ... hah ... Millenium Bridge (hard found lessons can be ignored to this day) things happen.
I'm no lawyer but I suspect the world of m'learned friends will catch up eventually. Until then we will read of silliness like this.