Please read the thread in that link. Someone asks him why he is hating on Arch, and he says, " because all alt coins created for speculation and fraud beginners and noobs this shit #ARCH $ARCH crash like other alt coins"

So he isn't basing his statement on anything concrete, just that all alts are the same and Arch will crash like the others. But clearly he knows nothing about Arch or he wouldn't make such a foolish statement.

That is just ignorance. Arch is clearly one of the best investments out there right now and there is really no rational argument to the contrary that I have seen.