[T-A]

> Perhaps the cold climate means people mingle less, and so social occasions are meant to reaffirm social cohesion, to the exclusion of airing differences.

My pet hypothesis is pretty much the opposite: until a century ago or so, these countries were quite poor, most people lived on farms, often far from neighbors, and for at least six months every year, anyone "nasty" enough to be expelled from the group was likely to be dead within days if not hours. So the "dissent gene" was weeded out.