I refuse to shed one tear over people letting religion affect them that badly. Nor give them the satisfaction that the DF'ing is working and that I am longing for a chance to communicate with them.
My unasked-for advice is to keep open to the possibility of that changing in time. In my experience, it has changed over time. I decided to walk away from them (my family), I did, then I changed my mind, attempted several times to reestablish any kind of relationship, didn't work out, and they are now out of my life for good.
However, before you say "then what's the point?" please keep in mind that those actions were taken by me FOR ME, not for them. As I grew older and wiser, I realized that making a definite decision about "shunning them back" was in fact, a decision made under the black and white mentality of the same cult that I wanted to be away from. It is important to make decisions by and for yourself, and as I lived my life I needed to revisit a number of ecisions I made that at the time I didn't realized were still influenced by that organization.
Furthermore, the indoctrination and brainwashing of that organization has absolutely nothing to do with the love I know some of my family members feel/felt for me. Those are things that I needed to experience and learn, and shutting the doors pr burning bridges behind you may hurt your growth as a human being.
You are 100% right about the cult and the attitude you should have towards it, but making such definite decisions around tour loved ones seems to be influenced by the very cult you want to get rid of.
Just my two cents.