Attack Of The Clones is a complete misnomer as they're not the attackers. If a B-Movie type title (which is what Lucas was going for) says 'Attack Of', you assume it refers to the enemy, but it doesn't.

And I know they eventually become the enemy, but for the purpose of the events of the film, it's the enemy of our protagonists that counts, surely.

It would've been a fine title had Lucas done what he should have all along and made the enemy forces the clones. Then we may not have had a mystery subplot that made no sense (the clones being made by the enemy, yet still being used by our heroes who never investigate it further) It would've made for a better film and a title that actually made sense.