Oxymoron. I have so often seen it used by well-informed people to mean "a stupid remark"
that I have been guilty of using it that way. Here is a sample from one of our erudite members:
"......All of which only proves that "female intelligence" is an oxymoron....."
By accident I just ran across it in a book of words, which made it clear that it is not always
a dumb juxtaposition of qualities. For instance: Chinese sweet-sour pork. Nothing stupid about
that combination.

Mostly I hear it used as though it were synonymous with "contradiction in terms". If you want to be hardline about keeping the purity of the phrase you should save it for phrases that are clever in their contradiction. It might be noted that the word oxymoron is itself an oxymoron, coming from the Greek words for sharp and foolish.

Dear Faldage: Here is a URL entitled "Oxymoron" of stupid statements atributed to Dan Quayle:
This how I got to thinking of an oxymoron, not as a juxtaposition of opposites, but a bit of stupidity.
http://www.greendomain.org/oxymoron_quayleisms.html