Scowcroft did say it, in August 2002:

In August of 2002, seven months before George W. Bush launched the invasion of Iraq, Scowcroft upset the White House with an opinion piece in the Wall Street Journal. The headline read, "DON'T ATTACK SADDAM." Scowcroft would have preferred something more nuanced, he told me, but the words accurately reflected his message.

OK, so he could have said it louder. He could have endorsed and/or campaigned for Kerry.

Of course, the media could have reported it better, too.