I'm not sure how you're going to convince anyone that increased merchant adoption through BitPay won't help contribute positively to BTC price but good luck dude.
They're not directly related. Especially not through Bitpay, as their service is based on 100% BTC selling pressure. Because all their merchants are paid in fiat. Buying anything through Bitpay = selling BTC for fiat.
Who buys the BTC that Bitpay sells? People who then become the customers who buy things through Bitpay again. It is circular; the buying and selling pressure cancel each other out.