Money, in whatever form, is a placeholder for a defined unit of power. You have a dollar, you can trade it to compel someone to do some amount of work, or give you something of value that they control. It only works if someone else values it. That goes for every form of currency, be it Bitcoin, a dollar, a piece of gold or a pile of coconuts.
I'm not a Bitcoin investor, so I have zero horses in this race, but I don't see why cryptocurrency is any less secure than any other transaction just based on the idea that it COULD have zero value in $SITUATION_X. It's value may crash due to speculation. It may not. Seems to me that I could say that about any form of currency.

Well, I know of plenty of people who do not find the exchange to be a fair trade(anyone who legitimately doesn't feel that they are paid enough but are forced by circumstance to take what money they can get), so I would argue that point. Perhaps a compromise would be to say that it can be either one.