There are some genuine national socialists within parties like BNP/UKIP but the thing is they 'poison the well' so to speak. Sorta like how all Trump supporters or leave voters are painted as immigrant hating racists.
I mean it's a shame really, that Trump supporters are painted as "racist redneck hicks who want to kill the blacks and spics" when in reality they are mostly working class people who haven't seen any change in their life and wanted some. Since Trump gave an outlet for the cause of neo-liberal policies (In this case, the wars in the middle east causing mass migration, and the war on drugs bringing in migrants from Mexico) which happened to point the blame at minority groups.
Although of course, many people don't even support him for that, but the mainstream media focused on it, painting a picture that elluded to that. So naturally, after years of being misrepresented by liberals calling themselves "progressives" or "leftists" they sway farther right as a reaction.
People are seeing the issues like you mentioned but aren't seeing anyone wanting to do anything about it apart from actual extremists or people labelled as extremists.
And even then, extremists are usually painted to be terrorists. But really it could just mean someone outside of the mainstream political system. I mean, people called Obama a Communist unironically at times.
tl:dr: Liberals are dicks who alienate working people. Extremists aren't always terrorists.
