Right. A nice JW couple. Elder and his wife in their 40s.
I was gone on errands to a nearby market. My wife saw them from upstairs looking for the ringbell (there is none). She opened the window and told them: "Knock and the door will be opened to you."
A bit startled, Mr. Elder hurries into the usual presentation. She replies: "I'm not interested, but my husband is a former JW. You may come back and talk with him when he's home." -- "Er, so you must have had a lot of visits already?" -- "Of course not, she says. You usually don't talk with former JWs, do you?"
At this point I arrive on my bicycle. "Hello, your wife just told us... we also visit our former companions... to encourage them to come back to the truth... maybe we are not here by chance, maybe it's the time for you to think it over... some people were discouraged by men but we must look to Jehovah... We have been JWs for a long time, we would not be there hadn't we been convinced through a thorough personal study of the Bible... God must have an organisation... the faithful and discreet slave as Jesus foretold..."
Well, I didn't feel like discussing a lot (had some cooking to do for a few guests) so I decided just to point out the circular logic in their speech. How each time they say "the truth," "Jehovah's organisation," "the FDS" they actually work out their own indoctrination. How they didn't really study the Bible in the first place but rather a catechism, with the WT questions and answers, with a convenient patchwork of "verses" designed to suit the answers. And then, when they do read the texts they have such a hard time making them fit into the catechism with the "help" of WT literature. How as long as they keep spinning like that no objection could really reach them. Because their system is consistent, even if it is consistently wrong.
And guess what? They did listen. That is, they didn't try to resume the WT speech after that and were just nice people with human words.
Maybe they have forgotten this already, but maybe some day they will remind this moment.
However, I found that this approach (pointing to their pattern of thinking) was way more helpful than discussing a specific topic in detail (which I might have done had I had more time on my hands).