[1.7.2] No Damage Arrow

I'm trying to spawn an arrow that does a lot of knock back, but no damage what so ever. If I set the damage to 0, it bounces off the player.

@Override
public void attackEntityWithRangedAttack(EntityLivingBase par1EntityLivingBase, float par2) {
	EntityArrow entityarrow = new EntityArrow(this.worldObj, this, par1EntityLivingBase, 1.6F, (float) (14 - this.worldObj.difficultySetting.getDifficultyId() * 4));
	entityarrow.setDamage(0);
	entityarrow.setKnockbackStrength(3);
	entityarrow.canBePickedUp = 0;
	//play sound
	this.worldObj.spawnEntityInWorld(entityarrow);
}