And if we use your co2 per mile approach we can all conclude that a rocket is the way to travel. People judge these things in terms of how much co2 is emitted

And if we use your co2 per mile approach we can all conclude that a rocket is the way to travel. People judge these things in terms of how much co2 is emitted by industry, companies, individuals etc. The particular mechanism of emissions is not that relevant. Air ambulance flights are treated differently to private jets carrying bankers.