You can find the relevant quote easily online by searching for "Heidegger" and "Spiegel". I think what is really going on is that Gray doesn't consider Heidegger's statement to be good enough.
--- On Wed, 7/9/08, B. <docile_body at yahoo.com> wrote:
> If Heidegger repudiated the Nazis, then someone should
> write a letter posthaste to John Gray, who is not a
> Marxist, socialist, or PoMo, and from whose book I
> quoted (_Straw Dogs_) about, and I quote,
> "Heidegger's never-renounced engagement with
> Nazism."
>