A public apology should start with a message to the people you directly wronged. Those indirectly affected also deserve an apology, yes, but the apology shouldn’t initially be directed to them.
At Grit and Glamour:
If you’ve always allowed comments, now is not the time to stop. It not only silences the people who are mad, but the people who might want to support you too. Plus, if you take away the ability to comment on your post, people will simply take to Twitter or your Facebook page to share their thoughts. Since you screwed up, you need to hear the feedback anyway. While some comments sting and are downright mean, for every one of those, there are three that are logical, or have ideas about how to make the situation better.
Relatedly, Jane at Dear Author updated her review of the most recent Lauren Baratz-Logsted (who wrote one of the guest posts for Plagiarism Week) romance with this note:
Updated: It is with regret that I add this addendum. Ms. Baratz Logsted wrote a post promoting the blog of a known plagiarist. We take plagiarism very seriously. I won’t remove the review, but I will provide this alert so that others can make a decision about how they want to spend their time and money.