User blog comment:TheTobarMethod/A New View On ADC's IMO/@comment-199.27.76.23-20130211163134/@comment-128.230.200.87-20130211200448

Just because a champion has an ability that they activate to do damage doesn't make them a "caster." An AD caster would be a champion whose PRIMARY source of damage is from abilities which scale off of their Attack Damage. If you consider any ADC with an ability that does damage you'd be considering literally every ADC as a "caster."