I think a single quote, even from someone as spurious as Kennedy mentions, is not enough to indict Palin. She may have been clueless about the source, more likely the speech-writer was careless in choice and application.

Context is everything, and since the words shifted to a new venue where most people hadn't heard of him (I've never heard of him) it acquires a new sense of meaning. Did she say "and in the words of the avowed racist Westbrook Pegler" or did she even name him? Were there enough of the words in textual order that Pegler used them they can actually be linked back to him and only to him, or is it a throw-away quote that is also used, for example, by Billy Graham or Pat Robertson?

There are a lot of good quotes and epigrams out there that have been laundered by various literary means, or so closely honed that the context can be dropped. Kennedy may be remarking on one of those.

SRS

The public is wonderfully tolerant. It forgives everything except genius. - Oscar Wilde