When one of my witness friends found out I was gay their exact words were, "You know my friendship is unconditional right? There is nothing you can do that will take that away."
That was about four years ago and I still can't help but tear up a bit everytime I think about it. Anyway, I think actually calling them and speaking with them would be MUCH BETTER than a text. Let them know that they have a friend in you and that your going to be there for them no matter what. I would also discourage asking why the got DFd. If they're comfortable sharing they'll bring it up. But chances are since its still so recent they're probably still a little shell shocked.
I would also strongly advise against talking about the society on your initial contact. Right now they need a friend and a sense of normalcy. Talk about that one time you guys were at that one place and that really funny thing happened. Talk about the latest episode of whatever. Just be a friend. You'll have plenty of time to talk about debunking the WTBTS later.