Those who are absent are always wrong.

This is what the proverb means:

When two people have an issue, or fight, or quarrel, etc., and they are to appear before the elders, the teachers, the chief, or the court to resolve the issue, the one present tells his part of the story as though he was right and innocent, pinning all the blame on the one who was absent and making him the offender and the guilty one.

This is what the proverb wants to say to all of us.