Everone has made some really valid points, so thanks for that. I can tell I will be speaking to a lot more people on here, it is quite comforting. I did not realise there were so many ex witnesses!!
Basically the guidance seems to be to use their own literature and the bible and let that do the talking. And not go in too hard. Trouble is, I left over 10 years ago as a teenager. It all seems to have changed so I don't even know what they believe in anymore. I remember "those that have seen the beginning will also see the end" being drilled into me, but apparently that is not "current thinking".
So now I have the problem that I don't really know what they believe in, and secondly, and am not that familiar with the bible.
I was going to try and stick to something that I do know about, such the history of human migration, cavemen, evidence that modern humans are many tens of thousand years and have very primative origins (not going into evolution at all as I am not sure where I stand on that myself). But I am stuck before I start because I know they will not watch the tv programmes and all the evidence will be ignored. I don't know enough about how they worked out that we have only been around for 6000 years, or even if that is still current thinking. My knowledge on the scriptures is very limited.
It is not my intention to make a personal attack. If they wanted to believe in the spagetti monster or a teacup orbiting the earth, all good to them. But they don't just leave me to my life, I am living in sin as I am not married, I am going to die in the end of the world, and they are not interested in anthing I have to say about anything that interests me. When I go to visit, its like, what can we talk about today, the weather? Not only that, when I do go to visit, they still carry on with with their theocratic activities and discussions as if I am not in the room. So to be fair, it is not me who is doing the attacking. I have just decided that next time they either try to convert or condem me, I am not going to just sit quiet and take it. If it is them that take the initiative, I don't see how they can justify "shunning" me. Still reason is not reason with people who can not reason.