Who was the recent guest on Bill Moyers' NOW show on PBS-TV,
self-proclaimed lesbian, speaking about the progressive thread in
Islamic history?

Hello.

I believe that you're thinking of Irshad Manji.

See:
NOW with Bill Moyers:  Author Irshad Manji
http://www.pbs.org/now/society/manji.html


Here is excerpt from a transcript of the show:

"MANJI: ... I discovered in theory at least, a progressive side of Islam."
source: NOW with Bill Moyers
http://www.pbs.org/now/transcript/transcript302_full.html

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search strategy:
lesbian islam moyers
"Irshad Manji", moyers

I hope this helps.