I am medically fit,clear of any dangerous criminal history,trained in my role and aware of health and safety issues plus the legal issues of having a bus in public service on the public highway.
So why do passengers ignore and or abuse me when I say "sorry i already have two buggies on board,you can come on but you will have to fold it" or "sorry i can only take 10 more" or "sorry you cannot stand at the front".
How easy would it be to kill a baby in a buggy when it is in the wrong place on a bus?
How easy would it be to pull out in front of traffic you cannot see because passengers are standing in your line of vision?
Overloading on ANY VEHICLE can and will cause problems with steering and braking.

TFL's policy of referring to passengers as 'customers' is partly responsible for this. Some people no longer feel they have responsibility to behave in a responsible manner or abide by PCV regulations that apply to passengers. Mere ownership of an Oyster card apparently, to some, means that they are entitled to travel no matter what.

Additionally, you are responsible for the bus you are driving and the passengers travelling on it, TFL don't really care how strictly you apply the regulations until of course something goes wrong in which case you are on your own if you have stretched or broken the rules.

The best policy is to stick to the rules as much as you possibly can, passengers may not like it but you can always ask them what they would do in your position, maybe it will make them think.