"Scratch an actor... and you'll find an actress"
The implication of the quote, as used in context (a discussion of a fight scene) was obviously that actors (male) were actually soft, over-emotional, perhaps even weak... like actresses (women). In short: Women are weak, and men who act are actually weak as well, the men merely wear a costume of masculinity.
The conversation about the fight scene begins at 9:00 in the audio. The Dorothy Parker quote happens at 10:22. (Audio of the interview is available at the top of the article linked above.)
Interviewer Terry Gross pounces on Norton's use of the quote and doesn't let go easily.
"Can you explain that to me? I don't get that, honestly I don't get it."
[Pause, as Ed Norton mumbles]
"Is that that actors are effeminate? Is that the joke?"
[Norton responds a bit...]
"Oh, so we're equating women with vanity, are we?"It was a pleasure to listen to Ed Norton attempt to dig his way out of that thread, and you could almost hear the sigh of relief when Gross moved on to the next topic (finally!)
I've not run into the quote before, but it seems a perfectly reasonable one... as long as you are someone that takes a traditional, and I would say reasonable view on the inherent differences between men and women generally.
But tread carefully if you want to be 'in the club' on the Left...