Do we have further details from other sources? Well, yes; CAMERA claims that King's words were pronounced "in a 1968 appearance at Harvard." Is that so? Er no. On the day of his death, the Harvard Crimson (the university's students' paper) reported:
The Rev. Martin Luther King was last in Cambridge almost exactly a year ago--April 23, 1967.
So that CAMERA is wrong on this (which, by the way, debunks the often-made claim "CAMERA may be biased but it's always factually correct"). All other references to the King quote are either explicitly based on Lipset's article or verbatim transcriptions without attribution.
The Wayback machine is a site that stores screenshots of webpages from all over the Internet. The sites are periodically scanned for changes, so that given a certain page you can know the full history of changes made to it. Up to 17 June 2009, the CAMERA page I linked to contained the wrong information that the King quote came from a 1968 appearance at Harvard, as can be seen in the Wayback snapshot from that day.
Then on 26 February 2010 the CAMERA page was modified. The reference to the exact year of the King quote was deleted, and the following text was inserted:
An earlier version of this article attributed Dr. King’s comment to a 1968 appearance at Harvard. To clarify, professor Seymour Martin Lipset and Congressman John Lewis, a disciple and associate of Dr. King, both point out that the comment was made in Cambridge shortly before King’s death, and did not name the precise date and venue.
To the best of my knowledge, no one had called out CAMERA over its inaccuracy before I did. I think I'm not wrong if I say that it was my post which forced CAMERA to correct itself.
Is this important? Yes, it is important, because it proves that CAMERA does not check its statements for accuracy, and because that leaves us with no concrete detail, let alone solid evidence, as regards the claim that MLK ever equated anti-Zionism to antisemitism.