Google being add supported doesn't directly raise the cost of competing services. Conversely Facebook making a deal to make accessing itse service free on a paid network has the direct consequence of making the cost of using competing services go up. The cost of free access to Facebook has to be borne by somebody, if not the ISP then the customer has to pay it when they acess non-subsidised sites.

Internet.org is not about giving things away for free, it's about a cartel using their combined market power to negotiate subsidies and fix prices in order to distort the market.