There are in fact a disproportionate number of white supremacists in Portland; Oregon itself was founded as a whites-only state, and it was illegal for black people to live there until 1926. The state's constitution on admission to the Union carried a black-exclusion clause.

Portland itself outlawed black residents in the 1840s and that law stood for many decades. It's only very recently that Portland has developed the reputation for having a liberal populace; as recently as the 1990s it was essentially the white supremacy capital of the west coast.