I thought I was moving on well but this is shaking me. I literally feel nausea over it. Damn the Borg for having this sort of power over me!
Mad Sweeney please don't be too hard on yourself. I know exactly how you feel! The number of times I, and many many others I'm sure, have had to dodge difficult questions as a result of JWs finding out about our former connections with the WTS. Believe me, if you don't tell them yourself they often seem to find out somehow.
The important thing is, don't let them fluster you. Calmly and politely say you hope they will understand if you don't talk about it right now, then change the subject. They should eventually get the message and leave you alone. It usually works for me, anyway.
Blondie's advice is good about rehearsing some responses ready for the next time it happens.
When they are really persistant to the point of rudeness I tell them calmly and with a smile that I have close JW family members to discuss it all with should I ever feel the need, which is very unlikely, so can we please change the subject now! I then start talking about something mundane like the weather.
You will find it gets much easier as time passes