You didn't define what those assets are, you didn't acknowledge that central bank solvency works nothing like a regular corporation, you called QE "money printing" rather than an asset swap (showing your lack of practical knowledge even more), you redefined the meaning of fraud, and you act like the most powerful government in the world demanding its citizens pay a yearly sum in those same dollars isn't a form of backing. You fail to acknowledge the ECB serves the same mechanical function as the Fed, you fail to acknowledge that central banks are a slave to demographic forces and thus the supply/demand for capital (aka money) and try to follow a natural rate, and you fail to understand the most basic functioning of modern currencies in the most mechanical ways - ways that are openly explained by the same aforementioned central banks in white papers on their websites. You also act like their function as a lender of last resort in the event of runs on banks caused by maturity mismatches that tend to happen once every few generations isn't explicitly and historically one of the primary reasons for their continued existence - your "purge the system" rhetoric aside, society seems to be ok with the banking sector not getting wiped out when things like that happen, because most people aren't naive enough to think anything good comes from total economic collapse. In fact, the same country you seem to hold up as a bastion of responsibility ended up with a collapsed economy within living memory, but no, it all turned out for the better... Yeah, I wonder why Europeans ex-Germans are pretty sick of German economic logic. (Brexit.)
As for relative credibility, at least the Fed didn't try to raise rates in 2010/2011, causing a further recession and much of the ongoing troubles there. German arrogance and 19th century moralizing-economic thinking is actually one of the major forces holding the continent back, while the US continues to shine.