Not to use a simplistic analogy..but..
I have NEVER in my life placed my hand on a hot stove burner. My parents told me when I was young that it was hot and would burn me. I know burners are hot by the fact that you cook things on hot burners. I have burned my finger on something else that is hot.
But I have never experienced my hand being burned by a stove burner.
Does that mean it isn't proven? I can't actually say that placing my hand on a hot stove burner would burn my hand since I have never actually done it?
Or do I use the fact that my parents explained it to me, I have witnessed other things to back up what they told me; i.e. hot burners cook things - must be hot, I have burned my finger on other things, etc?
I take all this information and formulate my opinion. I can say the same things about Crystal-meth, heroin, driving into a brick wall at 75 mph.
I don't need to have something "done" to me for me to know it is true.