The phrase "asserted something" is correct and usable in written English.
It can be used when someone is stating or declaring a fact, opinion, or belief with confidence.
Example: "During the debate, she asserted something that challenged the opposing viewpoint."
Alternatives: "claimed something" or "stated something".
When it introduced the original version of this vehicle, Porsche asserted something to the effect of, "The Cayenne Turbo plays the Range Rover's game off-road better than the Range Rover plays the Cayenne's game on-road".
When another asserted something that I thought an error, I denied myself the pleasure of contradicting him abruptly, and of showing immediately some absurdity in his proposition; and in answering I began by observing that in certain cases or circumstances his opinion would be right, but that in the present case there appeared or seemed to me some difference.
A physician asserted, "Something pops up, gives you a little tutorial it has to be short and sweet, something you can read in 30 s .And another explained, "You want to provide a little more information, but you can't have it so long, in providing every explanation….
For after all, if truth is a norm of assertion, then, if you assert something false, you are open to criticism.
"I can't commit legal malpractice by not asserting something because I'm in a wheelchair," he said.
If you want to destroy public confidence, solemnly asserting something that is obviously untrue is a good way to start.
Atheists and theists are identical in one respect: they both assert something about which they know nothing.
David Donald asserts something like the opposite in his biography: "At about the time of Willie's death Lincoln's optimism about military affairs also began to vanish".
"It's one thing to have information in a classified document with caveats and footnotes, and another to have the president flatly assert something," an intelligence official said.
"The truth is, this commission really did not have access to the type of intelligence that would have been necessary to indisputably assert something new".
All of which is further evidence for the wisdom in that line from Hamlet about the lady protesting too much: strenuously asserting something is often a sign that, really, you doubt it, or believe the opposite.
