I suspect the main reason he was attacked by Taleb was this misuse of language, which can be misinterpreted as meaning a 50-50 chance. Like others have said, he could have said "far from impossible" or "entirely possible" to convey that he meant the estimate had a large variance. Then again, I think Taleb should have realized this and not attacked him for simply failing to convey variance correctly. This seems like another example of Twitter bringing out the wrost in people...