The facts here are simple. BTC price is dependant on USD and it can be seen by merchants not willing to accept BTC without BitPay converting them right to USD.
Now, go, run boy. Buy yourself a brain and try to debate that.
How does "being able to change BTC for X" --> "BTC is dependent on X"
In your "logic" couldn't you say that the BTC price is dependent on JPY too?
Of course merchants (and especially those with low margins) will want to have the smallest exchange risk possible and for now exchange BTC for the lower volatility currencies (ie traditional fiat).
But more importantly, how do you think BTC gets its price?