What a ridiculous argument this is.
Since most of you have no idea what you are talking about, I will clear some things up.
The anti-lock braking system is designed to help the driver maintain steering control under maximum braking by preventing the wheels from locking from excessive brake pressure in emergency situations. It is not designed to make you stop faster. Although on some surfaces, this is a side effect of the system. I won't go into specifics but it's all about forces, rolling and sliding friction, etc etc. On a dry asphalt road you'll stop faster with locked wheels. On a very wet asphalt road you'll stop faster with ABS. On ice you will stop faster with ABS. On very loose gravel, snow, mud etc, you will stop faster with locked wheels, and on these particular surfaces it will take what seems like a lifetime to stop with ABS.
Simply put, ABS is there to help you brake really hard and steer at the same time. It's not to stop you faster.
Yes ABS does work in reverse. But I don't see the need for it to. If you find yourself in a situation where you are going backwards fast enough to warrant the use of ABS then you've severly messed up somewhere, and in such a situation, locked wheels would probably help you more than ABS. Remember, ABS helps you brake and steer. If you're going backwards at 50mph, why on earth would you need to steer? You'd want to stop as fast as possible, and if you're in a spin, ABS will not help.
And the system does of course have its limits, as I found out the hard way when I may have taken a corner too fast on a country lane, I went into a spin and ABS could do nothing to help me, only the wall that I hit could stop me then. Situations like that are where you want ESP, to prevent the spin in the first place.