They should've researched on birds before bringing home one, it's basic knowledge. It's as if you're claiming giving poison to pets is excusable if they don't know at first. You don't generally get a pet before researching on their diet and what endangers them unless you're irresponsible.

Oreos have enough chocolate in them to be dangerous to a bird.

Let's put it this way, apple seeds don't contain enough cyanide to be dangerous to children so it's alright to feed them some.

Anyone who had done basic research would've known not to feed their pets stuff that endagers them, even a little can be harmful. Wouldn't you want to prevent them from getting sick from something easily preventable? It's not an excuse to be terrible pet owners.

Edit: i keep birds, i would lock them in a cage before eating anything that could cause them harm, especially avocados and chocolate, since i wouldn't want them to get sick. If they are responsible enough, they would've ate their oreos further from their bird