This should come as no surprise to anyone, but...
I you want unfettered Free Speech on the internets, start your own ISP. There is a reason Yahoo and others have a thing called "Terms of Service." Those are... wait for it... the TERMS OF SERVICE.
You agree to those terms and that includes policing of content.
This isn't a free speech issue for Yahoo any more than it is for CC. The owners have the right to manage their services as they see fit and how the users AGREE.