> Not at all necessarily - this is what allyship is all about.
That doesn't really work. It means that you have to disguise support for your cause by spending most of your resources to support several other causes which may themselves already have more support than yours.
Moreover, "mix your money into a pool of money from other people that then goes where you want it without anyone being able to tell who sent what where" is basically how money laundering works. If that is allowed then you might as well abandon the pretense of tracing the money to begin with, because the "bad guys" will just do the same thing.
> Some funding sources may be illegal, and I would hope that tracing advertising to foreign intelligence agencies would do something to discredit it.
That is still basically an ad hominem attack. If the Russians get hold of Clinton's emails and release them, the fact that it was the Russians releasing them doesn't do much to disprove that she wrote them.
Moreover, if the funding source is a foreign intelligence agency, it's not as if they're going to file a disclosure statement saying "Funding Source: KGB" instead of using the name of a cutout. You have to prove it was them using some other means than what they disclosed, which makes the disclosure requirement pretty useless at catching the bad guys while still imposing real costs on people who are not doing anything wrong.