There is a dilemma here.

On the one hand entering into a debate with people who deny that the holocaust took place can be taken as implying that the deniers have a case worth debating.   

On the other hand refusing to enter into a debate, and setting up laws against holocaust denial, can also be seen as implying that they have a case, which has to be suppressed, because it might win in a debate.

A further complication enters into it, when the matter of the reality of the holocaust of Jews gets elided with other issues, such as the fate of other groups of victims and the question whether this is sometimes marginalised; and also the impact awareness of the holocaust continues to have on the way actions of Israel in relation to Palestine and on Palestinians have been interpreted.

These are very different issues. Unlike the matter of the reality of the holocaust, there are genuine questions to be explored and debated.

However it is evident that holocaust deniers are liable to seek to associate such questions with their own perverse enterprise, as a way of getting some credibility. And sometimes it seems that other people, who would sooner avoid these issues, prefer to see them associated with holocaust denial, as a way of avoiding them.