Jonah Goldberg and Dan Hannan MEP are expressing outrage that fringe individuals and groups like the Holocaust Museum shooter and the British National Party are routinely described in the media as "extreme Right". This, they say, is a slur on mainstream right-wing movements.
At one level they have a point. "Right-Left" or "Conservative-Liberal" gives one only one dimension to work with, and trying to squeeze multi-dimensional attitudes and perspectives on to it is bound to cause problems.
But is it really as difficult to come up with a meaningful interpretation of right-left for the situation of extremists as Goldberg and his readers think? There's nothing especially original about the notion that right-wing=backward-looking and left-wing=forward-looking, but it gets you a lot.
Right-wingers of every stripe are inclined to think that from an institutional perspective, things were better in the past than the present, or are better in the present that they would be in the face of various changes in the future. Left-wingers of most stripes are inclined to think, by contrast, that institutions have gotten a lot better or could be made a lot better. This is not to say that right-wingers don't accept material improvements in the quality of life. But they do think that values and mechanisms have deteriorated -- to take obvious themes: law and order, self-reliance, "traditional" education.
The left is instead animated by a vision of alternative arrangements that could be quite different from the present. As a practical matter, outside of the counterexample of Maoist lunacy, you'll rarely see a left-wing movement looking back in time for a model of what society should look like. Hence the reason that no one is particularly bothered by the socialist-communist continuum since there is a philosophy of the need for change underlying both.
So let's take the BNP. Hannan and Goldberg look at their policy positions, which are essentially protectionist, and note that such interventionist policies are usually found on the left. Therefore the BNP is left-wing! But the driving philosophy of the BNP is that Britain is a worse place than it was before. Worse because of immigrants, worse because of the European Union, and on the fringe-within-the-fringe, worse because of the Jews. To belabour a phrase, it's a "reactionary" movement, one which harks back to a lost age of a white Christian Anglo-Saxon Britain. Take out the philosophy and of course you end up with a jumble of policies that can be easily packaged as "left". But then what's the point of the BNP?
And then the Holocaust Museum shooter. For him it's also a lost age, with the Jews and the Fed as the major culprits. A reverence for "tradition" and abhorrence of "change", albeit carried to a deranged conclusion. But without that last clause, he'd be described as a right-winger.