> In other words, it allows those that do not like copyright assignment to always get to where they want to be.
No, it does not allow them to ensure that their code is always copylefted, if that is their desire.
> If we really believe in our FOSS licenses - and we should, otherwise why use them - then they will preseve our freedoms in both copyright assignment projects or in non-copyright assignment projects. To say that there is something non-free or evil or wrong about copyright assignment projects, seems to imply that our FOSS licenses are deficient, if they cannot guarantee our freedoms.
This is flawed logic. Licenses can only affect (preserve freedoms) on code which falls under that license. Copyright assignment allows this code to potentially be relicensed under an entirely different license, this says nothing of the original license.
> But I wouldn't stop myself from contributing to a project that does have it, or prefer one project over another because of it. It doesn't matter to me, as long as both projects use an open source license. That's the important part, not copyright assignment.
This makes sense if you would be OK normally releasing your code as BSD, but not if you would instead chose only the GPL (or only another copyleft license). Surely you should be able to see how this would potentially be unacceptable to those who want their code to be protected by the GPL?