Just to say that I'm in the 'it isn't about Brexit' camp. It's about a general view of the world, and respect.
DH and I have disagreed over the years about politics, but we have always respected each other, listened carefully and thoughtfully, and we do, broadly speaking, have a similar world view.
In a some social situations, it may make sense to avoid religion and politics to enable everyone to have a nice time, or to get a job done. But a relationship in which we didn't debate things that are at the heart of our character and beliefs, seems sterile to me.