I've answered your question, now I have one for you: Did you even glance at the link?
I'm sorry, these epistemologically relativist arguments lead to utterly absurd conclusions. How does wikipedia work at all? How can we ever make judgements about anything?
It's bad Cartesianism. Just because we can't know something absolutely doesn't mean we can't know anything. Just because language changes doesn't mean there's no such thing as correct and incorrect usage.