I do think that being a good neighbour works both ways - we had quite large conifer trees in the back garden, dividing our semi from the attached semi. Over they years, as they got taller, I worried that they were putting next door's garden in shade. They never complained, but (as sun worshippers ourselves) we decided it wasn't fair; we completely removed the trees and planted a hedge instead. Once the hedge got to a foot above the fence, we kept it at that height. I think if the neighbour in the OP had complained to me that the tree was causing problems, then I would have removed it and planted something more suitable. It's all a matter of give and take; if I was doing something that was upsetting someone, I would try my hardest to sort it out.