"You don't need CC to claim copyright"
As you say, this is automatic under the berne convention. Nobody who knows what they're talking about claims otherwise, let alone claims you need to use a creative commons license.
"CC isn't what grants you any rights"
The copyright holder is who grants you the rights. The mechanism they use is a license document that sets out in un-ambigious terms what rights they're giving to you. Of course, they could always write the license themselves from scratch, but unless they're an attorney specialising in copyright law they'll likely make subtle mistakes. Artists, musicians and programmers are NOT attorneys and should if possible turn to an attorney for qualified advice.
"You don't need CC to share"
There's a few points here:
1 - You can still share stuff even if doing so is utterly illegal. Connect to your favourite P2P network or BitTorrent tracker if you want to share ANYTHING in an illegal fashion.
2 - You can only share a copyrighted work LEGALLY if you have permission to do so from the copyright holder.
3 - Copyright holders can be contacted in individual situations to ask for permission, but when the copyright holder wants to encourage sharing, this quickly becomes a burden as everyone must contact them to ask.
4 - The way to solve the problem in point 3 is for the copyright holder to put a notice on the work explaining what is allowed.
5 - Most copyright holders have only a laymen's knowledge of the relevant copyright laws and may make subtle mistakes if they write their own license document from scratch.
6 - Paying an attorney to write your license for you from scratch is expensive
7 - Therefore, it makes sense to use a prewritten license such as the creative commons licenses. You don't NEED to use them, but it makes sense to do so.
"CC in fact discourages the social injunction"
Pretty much every last CC license states that people need to be credited for their work. However, absence of the license on one particular work does not mean that the opposite applies. Absence of a license actually is equivalent to a notice saying "Do not reproduce in any form this work".
"Absence of CC in fact does not hinder sharing, but its presence certainly does hinder sales"
It depends on your business model frankly. Realistically, if your business model is the traditional one of charging per copy and you release the same work that you're trying to charge for under a creative commons license, you probably will see sales drop on the for-pay version. Making money from free (as in freedom) content or software is possible but requires changing from the pay-per-copy model to custom work, support, ransomware or another more sensible model.
As to "absence of CC does not prevent sharing", that's accurate in so far as there's alternatives to a CC license, but you still need some form of license to share someone else's copyrighted work legally.
"The absolute WORST thing that CC does, however, is to undermine commerce"
No, a suitable license undermines the negative effects of copyright law - an artificial construct, nothing relating to real property at all. With the exception of the "no-commerce" CC licenses (which personally I consider to be none-free and refuse to use), none of the CC licenses say "thou shalt not make money from thy work".
Saying that people willingly choosing not to demand a government-granted monopoly are working against capitalism is laughable.
"Once given, Creative Commons licenses are irrevocable"
So are most proprietary EULAs (not all sadly, but most of them). If someone can revoke the license, it's pretty much useless as they can revoke it from you at any time. In some ways this may be worse than not having the license at all, if you're misled into building on top of the licensed content and the original author then revokes the license you have to stop your own work completely. However, if there's no license at all you can say "if I use this it'll be copyright infringement" and avoid it completely.
"Creative Commons recognizes the right, among some of the licenses, of others to take your work and re-release it in modified form for THEIR commercial benefit but it doesn't have a way for you to release it to make YOUR commercial benefit"
You as the copyright holder always have the full set of rights reserved by copyright law. When granting a license to others you only give them some rights but reserve the rest of them. You are never limited by the restrictions you place in the license given to others.