I believe you are arguing I could always choose not to work. I wish to work for an employer and the employer wishes to work with me. In this hypothetical there is required membership with an unrelated party I do not wish to associate with.
If I wanted to go to a coffee shop and that shop wanted to serve me coffee but the mafia is standing outside saying I have to pay them before I can go in, they are in fact forcing me to pay or turn away.
If I wanted to go to a coffee shop and that shop wanted to serve me coffee but the mafia is standing outside saying I have to pay them before I can go in, they are in fact forcing me to pay or turn away.