[TR] Off topic electrical question

[KingsCreekTrees at aol.com]

Hi all;
 
Perhaps someone can settle an argument between my son and I?
 
When charging a car battery, I was always told to disconnect the  battery 
terminals first, then connect the charger. My son, who is 23, NEVER  
disconnects the battery when connecting a charger to any car. He things the  
principle of having to disconnects is pointless. I have since found out that his  
practice seems commonplace among his generation.
 
Anyone got any thoughts?
 
Tim