It's ironic that Pete St John should have chosen "I'm forever blowing bubbles" as the epitome of non-sectarianism. A long time ago (at least thirty-five years) before I was interested in keeping records of such things, a man from the then Irish Free State whom I had met in a Youth Hostel, told me that in his childhood he had been whistling or singing "I'm forever blowing bubbles" and had been told by one of his parents never to do so again - "That's what the British soldiers sang while they were torturing Kevin Barry."
I don't know whether it is true or untrue. Belief has nothing to do with truth.
What's sectarian is very subjective.