Your freedom of speech does not entitle you to free usage of any privately owned electronic communications system. Your freedom of speech protects the content of your message, but does not guarantee you free postage.
Stop with the analogies. We are talking about elements of law, not elements of what-ought-to-be that might be studied by analogy. Congress is without power to regulate communication, end of dispute. Congress cannot stop spammers any more than they can stop me from casting messages into bricks and mailing them to someone who is paying a package forwarding service.