How can parents be so irresponsible?

Mandi 😈💀 • Expecting #2 August '15!
A high school acquaintance of mine posted on Facebook that her daughter, who will be 2 in May, opened and dumped a bottle of black nail polish all over the living room carpet, and then locked her out of the house to where she had to call the fire department to break open the door.
It really irritates me when people think they can leave a kid unattended for long enough to not only find, open, and dump nail polish (toxic if ingested), but then the parent is OUTSIDE and the kid closes and locks the door?!?! What in the fuck are you thinking? If you really need to go outside for any reason or leave the room really, take your kid with you, or put them somewhere they will be safe and contained, and out of trouble. My son is never alone unless he's in his crib in his room or in his high chair with toys, and that's only for me to run to the bathroom quickly, or if I'm doing dishes/making dinner and I'm actually right there but I can't pay full attention to him. I really can't believe that people think it's not only ok, but FUNNY that these things happen, when they could end up HORRIBLY.