There was safety in numbers in praising Stalin when the full story about what he was responsible for hadn't become public knowledge. There was safety in far greater numbers when he had become a publicly demonized subject of fantastic exaggeration by people who wanted to sweep their own genocidal crimes under the carpet.

Zionism is different. It was a safe option for Americans to support its racism, thieving and mass murder when Seeger did that song, but it is still just as dangerous for them to oppose it. You can lose your career that way. Very few Americans have recanted their youthful Zionism in effective, public statements. (Chomsky comes to mind).

I don't think Seeger had enough guts to face the damage he'd done.