That is not true at all. The GPL was devised for a very specific purpose and that purpose has been explained and discussed at work.
Then this should be made specific and overt. If a relevant or necessary demand is missing from the license, the license needs to be rewritten to include said demand.
The term, "spirit," by its' very nature, refers to something undefined, non-specific, and acorporeal. I'm surprised that anyone who identifies as an atheist in particular, would be comfortable with using it.
I say again; if there is a "spirit," or an "ethos," associated with the FSF or the GPL, and such has heretofore been implicit and "intuitive," then it should be made explicit, specific, and tangible, so that there can be no misunderstand, and no excuse.
My understanding of version 2 of the GPL, as the clearest example, was that if I modify the source code of a work governed by said license, I must make publically available, both the unmodified source code, AND the source code of my own modifications, to anyone who asks for it, as a condition of using/developing said work.
My understanding was not, however, that I am required to subscribe to any other belief, whether it be political, social, or in any other form, that may or may not be advocated by the Free Software Foundation.
In other words, if I use the GPL, I need to provide source with binaries. That's all.
I do not need to worship Richard Stallman as God. I do not need to subscribe to the philosophy of Karl Marx or Leon Trotsky in general terms. I don't need to believe Stallman's self-aggrandizing lies about how the very concept of source code availability supposedly originated with him, and did not exist before him. Hell, I don't even need to like him, or anyone else associated with the FSF, as people at all.
All I need to do, is provide source with binaries. That's it. Nothing else.