Finrod and the Kinslaying

[The Saucepan Man]

It might be just for a member of a folk to feel a shame for what has been done in the past in the name of this folk. But even that must come from the individual it self and can neither be demanded nor imposed form outside.

If I understand correctly, Mr Hedgethistle was not saying that Sauron used the fact that Finrod was part of a race capable of perpetrating the kinslaying to defeat him. Rather, he was saying that Finrod's internal shame at what had been committed in the name of his folk weakened him in the face of Sauron's onslaught. Which is not to say that he was being held accountable by another for what was done, but rather that he felt shame at what had been done and therefore, in effect, held himself accountable.