I think 90% or more are ashamed, 99.9% could not make a good defense of their beliefs, I also have to inform you that 99.9978346723 % of all statistics are made up on the spur of the moment !
I too am ashamed to admit that I was a JW, with new acquaintances I think I would at first, if it was relevant, say I was brought up in a cult, not name it unless pressed. Who wants to have to explain the wacky doctrines once they have left ?
I haven't ,so far, had to mention it, religion doesn't feature much in most peoples lives here in the U.K, and even less in their thoughts, so it just does not come up in conversation.