I knew an individual who claimed that foreign languages (other than English) simply did not exist.

This person would change the channel whenever something they didn't understand was being spoken on television, since they were apparently operating under the belief that anything incomprehensible (to them) was "demon speak."

They even had a bizarre string of backwards logic to support their claim:

1. Christianity is the only religion.
2. People in foreign countries aren't necessarily Christian.
3. Those same people don't speak English.
4. Ergo, since Christianity is the only religion, those foreign people don't actually exist.
5. Since those foreign people don't exist, neither do their languages.
6. Thus, any apparently foreign language is a tool of the devil, meant to pull people away from Christianity.

Perhaps worse than the idea itself was the confident, matter-of-fact tone used in offering it. In much the same way that you or I would declare something mundane, this person simply declared that foreign languages were the devil's deception.

TL;DR: Las otras lenguas no existen.