Knowingly using dirty money is immoral, even if used for a good cause [with the expection of undoing what made the money dirty in the first place]. On a tier-list, it would be a D tier option, above things like stealing toothpaste from a walmart, but below scalping via artificial inflation.

The immoral part is via association. Even if you denounce what the donor has done, you are still allowing them to be partially responsible for any good that comes out of the work/research.

Desperation for funding has often led people to compromise morality for progress, and I struggle to judge what is the correct decision, even if the moral option is clear.