Exactly because each communication setting is different, in a number of them, switching to English unconditionally, which is what the parent was suggesting, is indeed an "asshole-y" thing to do.

> Sometime the most important thing is to be understood quickly

Isn't this exactly what I said, "Unless it's a literal matter of life and death to understand what the other person is saying without too much of a delay?"

> Deciding which language to use with which person is a taxing effort in itself, especially in a group setting

In a group -- yes. Else, you just sound lazy at best and like a person who doesn't give a duck at worst.

> On the other hand, if the goal is to build some emotional rapport, trying harder in the other person's native language is worth doing.

The goal is to just be a decent human-being who is at least sometimes considerate of others' wants.