Glocks are just like any other gun....if you are unsafe with them, there is a possability that you are going to hurt yourself.
I while back I was showing my father my new Springfield XD that I bought (which has a trigger safety like the Glock, but with the addition of a palm safety like a 1911). He's looking at the gun, holds it, and squeezes the trigger....CLICK! ........."you didn't have the safety on!!" he tells me.
Luckily I made sure to clear the gun before handing it to him.......but for some reason if there was a round in the chamber, he could have hurt someone really bad. You never squeeze the trigger of gun unless you are ready for it to go BANG! My dad is not around guns very much, so I guess he just wasn't thinking when he pulled the trigger.
Now if there was a round in there, and he shot someone on accedient....would it make my XD dangerous? All guns are dangerous....learn how to handle them safely.