This world is full of wrong and people behaving in a wrong fashion.
A person would run out of breath before they could say all of them.
That being said...
Watching someone spike a drink with drugs and not saying anything is more wrong. You have to tell the intended victim before they can consume the drugs which will incapacitate them.
On the forum here...ok...opinions are welcomed and discussed. But that doesn't mean that it's ok everywhere. And the opinion can be met with hostility and as an unwelcomed busybody.
So... when asked...you can then tell.