How do you stop correctly when the car in front off you slams on his breaks...
it all depends on the situation. First and foremost you should leave proper space between you and the car in front of you (5 car lengths for every 10 MPH).
Although this sounds like "a lot" do the math:
a car is ~12 feet long. at 70 miles per hour thats 35 car lengths. Thats 420 feet. At 102 feet per second (70MPH) thats only 4 seconds.
With 100% observation on the road that gives you enough time to safely handle the car to a safe stop. If you're distracted it takes ~3 seconds to respond to an emergency.
SO: moral of the story, dont tail-gate, pay attention.
Now, proper "stopping" techniques. If you plan to stop in a straight line (IE: theres a cliff on one side and gobs of traffic on the other and the car in front off you slams on the brakes) you will be forced to slam on the brakes in their entirety. This will use 100% of your traction to stop, thus being the fastest way of stopping. ABS limits this form of stopping so people can maintain control of their steering (we'll get to that next) which lengthens the amount of space a car needs to stop (because they are not fully applying the brakes.)
"Why ABS?" Most people are not properly trained to operate their heavy machinery (yes, i called a car "heavy machinery".) When they get into a situation where they are on a big empty road and a deer hops in front of them, they slam on the brake ans jerk the wheel. By slamming on the brakes they are now using 100% of their traction to stop, thus jerking the wheel does little for steering (ever seen those black skid marks sliding right into a side-rail? barely any curve to it at all? now you know why)...
By reducing the braking power provided, the unskilled driver has traction which is not being used to stop to allocate to turning. This aids in the "OMFG WTF?" moments where people slam on the brakes and jerk the wheel, but it harms in the "AHHHH!!!" moments where people have to slam on the brakes and keep the car straight in hopes of stopping in time...
Therefore, a car without ABS, *in the hands of a trained driver*, is the safest form of braking as they are the ones who arent texting while driving and understand the performance of their vehicle.
My qualifications: Driver's ed completed three separate times at two different schools with flying colors. Am I a "professional driver"? Am I "all-knowing"? no. But I'm further along than 99.99999% of my fellow drivers.