I do agree on the points you've raised but the reason why brakeless fixies are popular in London is because it's mainly flat and hills don't exist except for the outskirts of the city, but the cool kids don't go there
I have a fixie myself but I run both brakes and also have a set of crosstop levers because I run a 50 - 16 so braking with my legs is not very swift or good for my knees.
What I'm trying to say is given a low gear ratio and mostly flat terrain riding brakeless might be plausible but I've bin in too many accidents to care about being minimalist with braking
Oh and if you just wanted to ride home from the track brakeless is just plain stupid!
Flatulence for men the musk that lingers.