"absurd assertion" is correct and usable in written English.
It is typically used when referring to a claim that is obviously wrong or untrue. For example, "Her assertion that she could solve world hunger in a day was an absurd assertion."
But his absurd assertion that Mr. McCain has been "compelled" by the media to adopt this strategy doesn't pass the laugh test.
She added: "Mary prefers to live in denial of what she is rather than change herself," citing Mary's oft-repeated, and clearly absurd assertion, "I don't really smoke".
She refused to grant Jews any special status, even as victims, rejecting what she called the "absurd assertion of a kind of collective innocence of the Jewish people".
Whispered criticism of Twellman's game has zeroed in on his penchant for "only" scoring goals -- an absurd assertion in a game that can end the same way it began.
At one point he even claims that Daniel Ellsberg, who leaked the Pentagon Papers, "had certainly been briefed" on the fact that he had been wiretapped at the White House's behest, an absurd assertion.
Kenneth Lewis, the Bank of America C.E.O., made the absurd assertion to Congress that his bank had "no authority" to stop the bonuses, even though he knew about them beforehand.
"I was surprised that no one from the British Council was prepared to rebut these absurd assertions".
In his ruling, the judge, Nicholas G. Garaufis of Brooklyn Federal Court, called the case an "ill-advised prosecution" that included "absurd assertions" and fanciful arguments.
As were the absurd assertions that then Assembly Speaker Fabian Nunez is a Communist fellow traveler.
It's time we refuse to give any credibility whatsoever to their absurd assertions that increasing taxes on the rich will slow the economy by punishing "job creators".
"These extremists created a fake business, made apparently misleading corporate filings and then used false government identifications to gain access to Planned Parenthood's medical and research staff with the agenda of secretly filming without consent," Richards also wrote, "then heavily edited the footage to make false and absurd assertions about our standards and services".
