So Kant's ethics is a morality of evil, as is easily shown. To act from self-interest is to pursue some value, some good. To reject all self-interest is to reject all good, absolutely and in principle. When good is ruled out, what's left is evil. This is nihilism.
Nihilism rejects the good as such, heavenly or otherwise.
The saint who pursues heavenly bliss through pious observances and good works wins zero credit from a nihilist. Nihilism credits no-one who seeks, upholds or defends any good whatever. Nor can nihilism merely be indifferent to good, as is recommended by some codes. Nihilism is active evil with delusions of righteousness. So were Fascists.