The M4 remarks do tell us something about him and the wider arguments around immigration and this morbid fear of foreigners that seems to be dominating UK politics at the moment. But it is not only the quality of the debate that is in question - we should all be worried about what is not being discussed.
When I was a student engineer I wanted to build my own road car. I planned out how much it would cost, where I would buy parts, what would I use as a donor vehicle, how would I manufacture the bodywork and most importantly: what engine would I use? I didn't want to make just another kit car, it had to be scalable, and with my own engine.