Yep. And the Unanbomber, and the Weather Underground, and the SLA, etc. etc. etc. and all of their ilk are simply footnotes to history. The exceptions that prove the rule.
Of course it is Chris Matthews, so you have to expect that the idea of it being a right wing group gives him a tingle up the leg.
Actually, aren’t all those groups really “single issue” terrorists: They hate everybody who’s normal.