Great question! The Ares’ Warrior Chant is not intended to harm others in any way. However, it conjures up images to put us in a “Warrior mode” mindset, which can be helpful for specific situations that require assertiveness, or even agressiveness.
The note about not being for beginners means that the rule of 3, or “harm no one” is general advice for beginners. Once you’re comfortable with the basic rules, it’s up to you to decide whether you’re going to follow them or break them, depending on each situation, and that’s your responsibility.
Personally, I don’t believe in dogma, and I go by this saying:
Rules are for the guidance of wise men and the obedience of fools