Single-speed... I just don't get it

If i had to run one brake with a freewheel it would be the back, because you can use properly it in corners and low speed manouvers, and if it locks up you aren't fucked.

Its like on a motorbike, you use the front 90% of the time, and only use the rear for corrective braking in the corners, but it is this that makes you able to ride the bike safely. A lot of custom bikes only run a rear brake to achieve a clean look ( a bit like fixed gears), but use a big un and it its perfectly good on the road, though you do sacrifice some ultimate stopping power

Or just maybe learn how to use your brake? I don't ever lock mine up and I don't brake on corners as that is just bad riding.

Saying that, on BMXes I always just had a rear but BMX brakes are hopeless anyway and more for very slightly slowing rather than stopping!