Nothing new about that. Using the words "Glock" and "Manual Safety" in the same post always creates the same result.
Actually, my point of view has nothing to do with Glocks at all. It has to do with manual safeties and people's false opinions that they somehow make a gun idiot proof. How many accidental shootings do you see where a person uses the excuse of "I thought the safety was on."
Then when you compound the issue with the contradictory notion that the same person that cannot be trusted to keep their finger off a trigger can somehow master the act of disengaging a safety at the proper time without thought it gets even worse...or worse yet, to remember to put it on when it needs to be on.
You are far better served by learning the basics (none of which mention a safety) listed below.
1. Treat every firearm as if it were loaded.
2. Never allow the muzzle to point at anything you are not willing to see destroyed.
3. Be sure of your target and know what lies behind it.
4. Keep your finger off the trigger until your sights are aligned on target.
5. Be sure your guns are never accessible to unauthorized or untrained individuals.
If you cannot be bothered to master these techniques no safety in the world will make you proficient enough to defend yourself or safe enough to those around you.