Heh. Taking the approach that everything is relative. If I walk across the room, I'm not delusional enough to claim that in fact I stood still, while it was actually the rest of the universe that moved instead.
Everything I might consider buying is priced in US dollars. If the US dollar was fluctuating wildly like bitcoins are, the prices of everything those dollars would buy would be changing just as fast. The reasons that the US dollar is the default global currency include that it is relatively stable in value, and exists in large enough quantities that any transaction can be made in dollars. If somebody wants to buy 1,000 tankers of oil today, they can complete the transaction in US dollars. Could they do that with bitcoins?
The stability of the US dollar is determined by the prices of the universe of things it can be exchanged for, including other currencies.
Show me an example of something you can buy that is priced in bitcoins. As far as I know, everything you might want to buy is priced in dollars, but some places may give you the option of PAYING with bitcoins.
www.openbazaar.org
www.overstock.com
These sites let you buy anything with bitcoin.