Did you ever download a freeware game or application? You also don't necessarily know everything these programs are doing, yet many people with half a brain do download them. Even official software can contain malware, ironically some of it has come from Sony itself in the form of a rootkit on audio CDs.
I'm not playing semantics, I'm stating that something can't be an organization when there is no way to join it or leave it. By any definition of organization, that alone prevents it from being one. Yes, you can leave your job without telling anyone, but you most certainly cannot get a job at a company without the company knowing.
I don't think I can make my view any clearer...
I see you skipped the other examples I gave. Care to address them or just going to pick the example you think best suits your purposes? Book clubs can be the same way in many areas. Hell we had an unofficial club that turned official for minor funding video game club on my campus. Consisted entirely of anyone who walked through the room we were in and wanted to play the games we had on. Anonymous is a collective of cells, and there is a real organization there. They choose to associate themselves with all past actions using the name.
Also, I check what I download and install. Anything I don't fully trust, or can't find detailed information on goes to a virtual machine first to see whats what. Once I have proven its safe then it gets installed. That is still not remotely the same as intentionally installing malware though. This is like someone knowing the rootkit was on the cd, and then using it for the specific purpose of getting the rootkit there so someone else can use it in a malicious way.
What book clubs let you take stuff without even looking at you? I don't see anything different about the other examples you gave, that's why I skipped them.
The burden of proof is on you to prove that there's an organization which encompasses all of Anonymous. Good luck with that...
Your virtual machine won't necessarily stop the software from doing what it wants to do, especially if your virtual machine has network access. It can spread viruses on your LAN, etc. I'm assuming you don't reverse engineer all the software you download, so you're still at risk even if you run it on a VM first.
I don't think malware means what you think it means. If a program does exactly what it advertises and no more, it's not malware even if it does stuff that other people wouldn't like.