Arguments can be made that union lobbyists get laws and regs passed which benefit all workers.
Today there are lots of organizations that lobby for all kinds of causes. Why should one type of lobbying be given the support of government backing and forced contributions? Would it be appropriate for me to make a requirement for employment that all employees have to donate to the Sierra Club or the NRA?
The way I see it, unions were necessary to level the playing field between workers and business owners. Now they have served their purpose (and perhaps too well) so it's time they go the way of the dodo bird.