I think that it's a lot to do with conscience. I found that for me to be associated with Jehovah's Witnesses I felt I was showing my support for their views regarding 1914 and it's significance. One person suggested that I could maybe not mention 1914 sort of forget about it. I couldn't. It was from my understanding very significant to our preaching work. If I was not joining in the preaching I had to explain my reasons which I did and eventually it became better for me not to attend. Although that came at a cost of some friendships that we had in the congregation.
Sometimes we discuss whether or not we could attend again for the reason of associating with people we knew and were friendly with and have a bible viewpoint we were familiar with.
This we tried for a while some years ago and it resulted in discussions with some elders regarding different teachings and viewpoints.
The thing is that I would feel at this point a hypocrite to identify myself again as a Witness and this would go against my conscience. My wife and I along with my children regularly discuss christianity. I have some very close relatives that are very well read in theology and even if this were not the case there are plenty of books available for research along with the internet. I pray regularly and read the bible.
Of course I could be wrong with some things that I think and maybe your right that associating with like minded individuals can help to maintain one's integrity. I don't think it's a case of not being humble or presumptuousness, but rather it's a case I think of keeping a clean conscience by not being a hypocrite and this is keeping my integrity.