Oh yes they can, that question has been settled in the aftermath of the Yugoslavian Wars [1, page 148]:
> 46. The law is thus clear: a hospital becomes a legitimate target when used for hostile or harmful acts unrelated to its humanitarian function, but the opposing party must give warning before it attacks
That has nothing to do with your original statement. Yes, hospital can lose their special protection but must then be given a warning that gives them enough time to evacuate and only if that warning is unheeded, it loses special protection. But all the other rules protecting civilians still apply (distinction, proportionality, precautions, …). In any case, this has nothing to do with the whole civilian population being stripped of their protections. They still have their human rights and cannot be targeted.
So pretty much every hospital, school, and over 60% (nearly 300,000) residences have been destroyed in Gaza, leaving well over a million displaced. You are a genocide supporter.
> 46. The law is thus clear: a hospital becomes a legitimate target when used for hostile or harmful acts unrelated to its humanitarian function, but the opposing party must give warning before it attacks
[1] https://www.icty.org/x/cases/galic/acjug/en/gal-acjud061130....