I have no idea what the JW's are currently preaching, as I don't keep up with it.
But it seems to me over the years, when I was associated and having some relatives that still are, that the GB are always dropping little things in their publications, that suggest your conscience should be bothered if you are associating with anyone that used to be a JW and are no longer or even just inactive.
My devout mother is constantly jumping back and forth between speaking/not speaking to me and my unassociated sister, depending on how confused she is between her devotion to that book publishing company and her feelings of love for us.
Who knows if someone showed your father a older/newer publication that bothered his conscience in the same manner or it was more "new light." But one thing is for sure, be ready for a rollercoaster ride if you are starting to stray from them.