It seems to me this highlights a flaw in the payment system - the inability to decline. Am I understanding that right? You really can’t refuse an ETH transfer?
You can if you put your money in a smart contract that refuses all transfers that haven't been pre-approved by you, although that's not the standard procedure.
This makes it more difficult but not impossible. The EVM has a SELFDESTRUCT opcode [1] that will send ETH at that address to a receiver and it's impossible for the receiver to refuse. A very determined actor could send Tornado ETH to a contract designed to self destruct upon receipt of the ETH and relay it to the intended receiver.
You can program your smart contract to forever deny the use of such funds by recording its "non-selfdestruct" balance in the state and only allow to withdraw up to that amount.