That's just wrong. There are plenty of things you can do to avoid being attacked, however you need to know the attack thresholds of the specific leaders that you're trying to avoid being attacked by.
You can use diplomacy to boost relations to a threshold high enough to not get attacked by one specific leader, but you can't rely on not getting attacked at all during every game. IE, you can choose to adopt Isabella's religion, but you can't stop Isabella and Boudicca from creating rival religious blocks and having to choose to ally with one or the other.