I don't understand that argument.
If I use Facebook, it's easy to see when I log on/off to profile my usage (and possibly employment / holiday trends). If many of the people I speak to are young or gay or work in finance, doesn't that imply something about me?
I am not a fan of this Google policy (it leaves me very uncomfortable) and I support the protests. But, as far as I can see, I can opt out without being marginalized. That's the bit of your argument I cAnt understand.
Your argument, to me, appears to be that Google shouldn't be allowed to link you and your opinions to your real name. I'd argue "why not?" I don't use Facebook, etc for this very reason - I don't want to be profiled with the depth that Facebook allows. Am I marginalized? Not that I'm aware.