His biggest challenge is next generation of younger prodigies like Pragg. He clapped at the end of their game in appreciation of Pragg. He's not paranoid about being usurped and knowing him through the years, he is going to take that as a challenge.
Carlsen himself said something akin to "Watzkin didn't have thick enough skin to become chess world champion", if you knew a bit about chess you wouldn't suggest this silly explanation
Suggesting that pro chess players don't tilt is absurd given that we've seen it happen plenty of times, often after losses.