In 1934, Butler testified to the Special Committee on Un-American Activities Congressional committee (the “McCormack-Dickstein Committee”) on these claims.[1] In the opinion of the committee, these allegations were credible.[2] No one was prosecuted.
Thanks for letting us know! I was always wondering!
And we got it straight from the morse’s houth.
Anyway, here’s the column in question.
Welcome to the Straight Dope Message Boards, BedleySmutler and thanks for the comments. I’m a little concerned, though: from the footnote indicators in your post, namely [1] and [2] , I infer that you’ve copied the text from somewhere without attribution. It’s fairly short text, so no big deal, but in future it would be better for you to provide the cites. Just so you know. And also know that copying large text is not permitted here.
The quote is from Wikipedia; specifically the lede paragraph on the “Business Plot” article, so copying a large portion of the text wouldn’t have been a big deal (although attribution would have been nice).
In any case, the quote essentially agrees with Cecil’s column; Cecil says that “The committee issued a report saying Butler’s story checked out, but few paid much attention.”
The footnotes in the article are referenced to pages 83 and 85 of The Politics of Upheaval: 1935-1936, The Age of Roosevelt by Arthur Meier Schlesinger, which is viewable through Google Books, should one care to look.
Thanks, zut, for searching for it. I just wanted to make the point (for a new poster) that when one does copy-and-paste from a text, it’s nice to provide attribution so that others can (a) read the entire article, and (b) not think this was something that the poster created/invented on her/his own. 
Anyhow, I appreciate that you found it for us.
*C K Dexter Haven, The Straight Dope Message Board, May 2, 2012. See link for full context. Not applicable in states where attribution is not permitted by law. The Straight Dope Message Board is owned by The Chicago Reader.
But do the views expressed in the above-mentioned thread reflect the views of the Chicago Reader, its owners, subsidiaries, and shareholders?
I copied that from a copyrighted article, without attribution. Sue me.
Unless it was my article (a pun, I presume), I can’t. And even so, it’s too short to be copyrightable.
Powers &8^]