There's a very fuzzy line somewhere, on one side of which a provider is helping users get what they want, and on the other is blocking content they don't want users to receive. I'm exploring where that line is.
While you have a right to send emails to me, I have a right to sign up for a service that automatically blocks emails I don't want to receive. The line is crossed when that service starts blocking emails I would like to receive. I'd say there is a pretty competitive market of email providers, and the rules are reasonably transparent about what's being blocked. Thus, it seems that "censorship" is a rather strong accusation here.