This is why the statement from the FSF is so important, they actually own the copyrights to a very large portion of software that is redistributed by Red Hat, including, but not limited to:
* The bash shell.
* glibc.
* the gcc and g++ compilers.
* emacs
* Gnome ...this list just goes on and on. The FSF *has* standing to bring litigation against Red Hat for this, and as such their opinion on what Red Hat is doing is *very* relevant.
Now whether they can win in court is, as you say, not a given, but they certainly have standing to bring the lawsuit.
Also consider that if they *really* want to they can update the GPL again (GPLv4 anyone?) and start distributing their software under that, so when they say that what Red Hat is doing violates the spirit of the GPL they do have the power to bring the actual GPL into alignment with the "spirit" for which they refer. Now updating the GPL to a new version is a lot of work and certainly there would be consequences related to acceptance and adoption by the community at large so it's not a simple ask, and I really doubt they would do this just to gain leverage over Red Hat in this particular case, but they can if they really want to and it would be game over for Red Hat if they do, there is very little chance that Red Hat can release a quality product without including at least some GNU software in it.