I'm with Long Hair Gal on this, I feel no need anymore to inform JW's, I did, when I first left the cult, I thought it was Mission to give them any and all information, my Duty.
As I matured after leaving, I came to appreciate it simply was not down to me morally to do so, unless there were dire circumstances, and the JW was in some grave danger by believing, which of course can happen.
I now live my life by the Mantra "Do the least Harm and the most Good". Using that, if I ever get to talk to them, I think about the person and how what I say will affect them. For example, some of my older relatives who are JW would be lost and devastated without their Social Club, which is the only benefit they truly gain from it, but why should I make their life emptier than it is ? They would be lonely and sad.
On occasion when JW's have knocked on my door I have given them some real truth, if they come trying to shove their beliefs upon me, then I think it is fair to explain in a kindly and measured way why it is not for me. But I don't see any moral imperative to do anything normally, and sometimes I have simply said something like " It was kind of you to call, Goodbye". If I am too busy to have a conversation. Hope this helps.