"Christianity is true" and "Islam is true" are mutually-contradictory positions. "C++ is fit as a general-purpose programming language" does not contradict "X

"Christianity is true" and "Islam is true" are mutually-contradictory positions. "C++ is fit as a general-purpose programming language" does not contradict "X other language is fit as a general-purpose programming language". So your logic in your first non-quote paragraph doesn't work. [Edit: To respond to the actual point: For every claim that X is fit as a tool to do Y, the evidence that millions of people use X to do Y is in fact proof of the claim. If the claim had been "C++ is the best language for general purpose programming", then your argument would have merit. But that wasn't the claim.]