The matter is that what this poster says does not sound very credible to me, and you cannot change that.
Yes, that certainly is the crux of the matter. Both turnoi and silverbaby have this ability to settle on an opinion and stick to it like glue. It doesn't matter what is posted, if it is anti their view, it will be wrong, and nothing anyone says can change that! An open mind is not an option in the big, wide world of Language Teaching.