The claim made by Eliphaz was that the quran is in Arabic and, therefore, cannot be considered a message for mankind. The obvious problem with this stance is that the message of Islam can be conveyed without understanding the Arabic language. The core fundamentals of the faith - belief in one god, submission to his will etc can be expressed in French, Italian, English, urdu or any combination of the above. The fact that the majority of Muslims in the world today do not speak Arabic, yet still accept its message is at least partial proof of this.
Personally I've been pressured to read the book twice in Arabic as a child and I've not understood a single word, the exception being “Allah”. I, as well as many thousands of children are brought up to read Arabic and not understand it in the UK. So the theory that it can be translated in different languages really doesn't work in practice when many parents pay a fair amount of money (and it is not unknown in the UK for this funding to be obtained from a parent's child benefits allowance) in order to pronounce Arabic, because this is the
holy right way. And when they grown up to be adults, I think that you can be assured they are still not understanding a word they pronounce in Arabic (except "Allah"). EDIT: This is of course on the assumption they do not bother reading the translated verion. I don't know any Muslim personally who has.