The problem with allowing Disabled Drivers to park on Double Yellow lines means that non-disabled drivers are penalised and are being discrimated against. If there are areas where disabled drivers need parking and are parking on double yellow lines, then mark these parking areas for Disabled Drivers, otherwise let everyone park on them. It has to be fair for all.
Apparently, Double Yellow Lines are there on roads for safety. If so, why are Disabled Drivers allowed to park on them? Do Disabled Drivers parking on double yellow lines make the road safer? Of course not. So, if Disabled Drivers can park on them and not cause a road obstruction, and not be fined, why can't non-disabled drivers? Conversely, if disabled drivers are legally parking on them, why have double yellow lines at all in some places?