Surely at least some part of their stack is built using Python, so couldn't you tell them that they may not use the software if they are going to proceed with this?
Edit: if you're going to down-vote, at least read my clarification below.
Why would I build on something that lets the owner act against me with relative impunity (assuming the software is something critical)?
Furthermore, I think the problem is not here, the PSF clearly made a mistake by not registering the name (it's not a matter of 'bad law'). If we apply your solution, then it would mean that a company which does not use Python can still ask to register a global trademark named on the term.
You acquire some pretty reasonable rights in a trademark by virtue of use alone.