I used to work on Airport Security at a major UK airport. I can assure you that not only baggage handlers but every member of Airport staff, from Directors to Cleaners are very thoroughly vetted, prior to being accepted onto the payroll. Also if even a minor offence is committed by staff it is virtually a dismissable outcome.
You cannot imagine the stupidity of some passengers when being asked by Security what they are carrying, the 18 to 30's usually reply I have a bomb in my hand luggage, Great, another one arrested and sent down for 5 years.......the moral of the story, dont question why it is being done, just be grateful that in todays climate it is being done.