You’ve missed the point of the example situation. Throwing the jar at a person’s head isn’t one of the available choices.
You're missing the point of free will. Putting a limit on people's choices is the antithesis of free will. I can make the choice to use the jam to make a sandwich, I can sell the jam, I can throw the jam in the garbage, and yeah, I can throw a jar of jam at someone if I choose. Some of these options are better than others, but free will means I make the choice, the choice isn't made for me.
If free will was really so important to create us with, god could have done so in a manner similar to the humanized people from the book.
Free will is important since it's the essence of creation. If we didn't have free will we'd all just be an extension of God, not distinct beings. If there are no distinct consciousness, then it would be just God and nothing else. If there's no distinct consciousness then there's nothing really created. It would be all just thoughts of a single being.
For there to be distinct consciousness there needs to be the capability to make choices, which means there's there's the capability to make bad choices. For me to be incapable of throwing a jar of jam at you there would need to be an omnipotent being governing my decisions. But doing that would take away my agencies and destroy free will. Destroying things is the opposite of creation, which would be against everything God is supposed to be.
Just as we are capable of making choices, God is also capable of making choices. Choice is something that an omnipotent being should be capable of, right? God's choice to not interfere with our consciousness is inseparable with the creation of free will.
On the other hand, the false belief in a tri-omni god is in fact a prerequisite for a number of religions, and therefore are indeed weird superstitions deserving of mockery.
And that is your choice. God isn't going to stop you from making this choice. But is mocking other people's beliefs making the world a better place?