There is also a press quote from deRooy saying he was visiting an unknown doctor in Italy, and so the team decision is understandable.
It still raises the question that if riders have the means to cheat in undetectable ways, should you be able to change the rules and DQ them (not exactly DQ happened), even if you can't catch them cheating.
I think blacklisting some doctors is a good idea, but it shouldn't be done retroactively.