>I'm not asking for anything, I was merely pointing out the advantages of anonymity. You don't need to consider a decision the best one to see its upsides.

You haven't given any yet. You've pointed out that anonymous messages in some circumstances can be beneficial (which they can), but haven't given any advantages for a widespread, anonymous communications network with open access.

>Privacy in mail and telephone was a commonly supported right

It really wasn't. I don't know of any time or place where mail and wire tapping wasn't legal and/or practiced.