How do liberals get switchblades, if they've been banned since 1958?

Same way they get heroin.

You can get assisted opening knives. "Journalists" being not journalists and lazy probably just called it a switchblade. On the other hand, it was simpler than explaining what an assisted opening knife is.

You can buy one on BUDK. Owning one is not illegal.

The Act prohibits possession of such knives on federal or Indian lands or on lands subject to federal jurisdiction. It does not prohibit the ownership or carrying of automatic knives or switchblades inside a state while not on federal property, nor does it prohibit the acquisition or disposition of such knives in an intrastate transaction or an interstate transaction that is noncommercial and/or does not substantially affect interstate commerce (as defined by recent decisions of the U.S. Supreme Court).