Weird logic too. There's still 21m Bitcoin. Even if there was 10 billion XMR, there'd still only be 21 million BTC. Monero devalues Bitcoin in the same way an armoured truck devalues a G-Wagon. Apples and oranges.
Not if people use it. If people effectively use it to assign value to real world stuff, it effectively creates inflation for the market in general, making Bitcoin less valuable. More or less what happened with the US dollar and Bitcoin. They printed trillions of USD, but Bitcoin keeps its price trend as if nothing happened, it didn't double in price or anything. The Fed effectively pushed Bitcoin down by having people use it.