"You have to respect his decision to become a priest."
Translation:Du måste respektera hans beslut att bli präst.
Should "Man måste respektera hans beslut att bli präst." not also be accepted? The "you" could easily be the impersonal "you" in English, in the absence of any context to suggest otherwise.
"Ni måste respektera hans beslut att bli präst" is an accepted translation, but should it be? The English sentence mentions "a priest", not "priests".
More generally, do Swedes always use "ni" when addressing several people (e.g., as an author or broadcaster) or do they sometimes use "du" as if they are addressing each person individually?
?? There's only one priest in your first sentence, so I don't really understand what you mean? bli präst means 'become a priest'. Multiple priests are präster.
We always address groups of people with ni, never with du. When we say du, we're always addressing just one person.
It's possible to use ni as a so called polite pronoun when talking to one person, so that works too.
In Sweden, it can be a bit controversial to use ni as a "polite" pronoun, some people strongly dislike it and some may even be offended. Most people just don't use it that way. In Finland, it doesn't seem to be controversial, but it's never necessary there either.