However a spent address has only ECDSA separating your money from the thief, and it's very scary.
Yes, a spent address has only ECDSA separating your money from the thief, but no, it really isn't scary.
So I think public keys should be treated confidential as well as private keys, in the sense that newbies should not reveal them to strangers.
That is only possible if you NEVER re-use an address. You should generate a new address EVERY TIME that you receive bitcoins.
Otherwise, the public key is right there in the blockchain for the whole world to see as soon as you spend an output that was received at the address.