To support another countries foreign intelligence service (which is targeted with espionage on Germany) is nothing short of treason on an organized scale.
Maybe, but the logical slippery slope if you do allow this happen is that in the end every country cooperates and their budget for counter-espionage looks like... the budget, say, California has to defend itself from Texas and Massachusetts, or for securing its borders from Arizona, Nevada, and Oregon by planting spies in those countries I mean states, or the FBI budget for counter-intel versus the CIA. All of which is exactly, precisely $0.
In what conceivable world is it better for California to be spending that money on such hypothetical programs, or for taxpayers to fund the CIA in its attacks against the FBI, and to fund the FBI in its countermeasures against the CIA -- an idea that is total, complete madness - instead of putting it into education, roads, water, or whatever else you want that actually has any benefit to society whatsoever?
The world is incredibly well-connected, and states don't need to be hacking other states. Whether you agree with surveillance or not, it is not difficult to argue that cooperation is a net benefit for all.
Then of course, foreign intelligence services derive their power and existence outside of the normal law framework from the simple fact that they are generally not allowed to spy on their own (e.g. US) citizens. That is pretty much the very fine line that separates them from a state-funded terrorist conspiracy. In that light, any cooperation with another intelligence agency (which naturally isn't bound to not spying on US citizens) is prima facie suspect.