Why did Mikael Blomkvist not have any moral concerns about hiding the identities of two serial killers?

In the book, when Dirch Frode asks him (on behalf of Henrik Vanger) not to publish his story, Blomkvist specifically notes:

I don’t intend to hang Harriet out to dry, but somebody has to say something about the women who died in Martin’s basement. Dirch, we don’t even know how many women he tortured and slaughtered. Who is going to speak up on their behalf?

Lisbeth notes his dilemma and offers the following compromise:

Martin videotaped his victims. I want you to do your damnedest to identify as many as you can and see to it that their families receive suitable compensation. And then I want the Vanger Corporation to donate 2 million kronor annually and in perpetuity to the National Organisation for Women’s Crisis Centres and Girls’ Crisis Centres in Sweden.

Therefore, Blomkvist did express concerns over the morality of his actions and was reluctantly mollified by Salander's compromise.

I'm not sure if this made it into the English film adaptation. But I do vaguely recall a scene along these lines in the Swedish flick.

I think it would have become more of a moral question if the culprits were still alive and out in the open. Blomkvist did not reveal these facts because that would attract stigma for the whole Vanger family. Also if things were dug up, the fact that Gottfried and Martin abused their own daughter & sister respectively, would become public knowledge. This could also have affected family business.

Also in my opinion Harriet Vanger had had enough and it was better for her that these things were buried. So Blomkvist suppressed his moral concerns to protect Henrik Vanger & Harriet Vanger.