The Internet of criminal things

I think the ultimate counter-argument to this is that you can already trivially put whatever liquid you like into your fuel tank (or even worse, the oil filler on top of the engine or indeed the brake or steering fluid reservoir), and somehow most of us still manage not to pour things in there that put our cars or indeed our lives at risk, and nobody is clamouring for padlocks or security caps to be fitted. (Yes, I'm aware that some cars have internalised or removed some of these filler caps, I don't think I would buy such a vehicle.)

Sure, that's not nearly as complicated or perhaps as subtle as modifying code in the ECU - but that's part of the point - it's trivially easy to do the wrong thing here and yet most people don't even have the inclination to try something they shouldn't.