A man of great integrity? Perhaps he was, but there's no evidence of it in that post. I see only evidence of his being socialist, which I do not think says anything about integrity either way.
And the Patriot Act, ACLU hysteria notwithstanding, does not allow the FBI to maintain files on individuals. Indeed, due to past over-reaching, the FBI is specifically forbidden from maintaining files on people solely because of the exercise of their First Amendment rights. The people must first be reasonably suspected of involvement in criminal activity.
Cindy Sheehan's being vilified by FOX NEWS is par for the course for that station, the National Enquirer of right-wing TV. They're wrong, but no one takes them seriously except the truly committed hard right who cannot hear reason anyway.