Bill Maher said the same thing about Nancy Reagan last week in his show. I don't remember Sanders supporters asking him to apologise.
Is that really the best you can do? Even if he did say that, he's not running for President and not relevant whatsoever to the 2016 race, but you know that. Also, the biggest outrage I've heard personally around Clinton's comments came from Clinton supporters themselves asking for her to apologize immediately.
He is a vocal Sanders supporter so don't give me that BS about him not running for president.
Except he really isn't running for president, he is barely relevant at all to this race, and it's not just Sandernistas who are angered by this.