The reentry tech in ICBMs has nothing to do with satellite disposal, and, in fact, would make satellite disposal more hazardous (because it would mean the satellite would reenter in one piece rather than breaking up into smaller pieces that are more likely to burn up/melt in the atmosphere).
An ICBM warhead reaches space but at suborbital speeds. It never reaches orbital velocity and will reenter no matter what; it has a heat shield so that the warhead remains intact when descending through the atmosphere.
For satellite disposal, the satellite starts off at orbital velocity and needs to be decelerated above the atmosphere to drop the low point in the orbit far enough that the atmosphere will decelerate it below orbital velocity.
An ICBM warhead reaches space but at suborbital speeds. It never reaches orbital velocity and will reenter no matter what; it has a heat shield so that the warhead remains intact when descending through the atmosphere.
For satellite disposal, the satellite starts off at orbital velocity and needs to be decelerated above the atmosphere to drop the low point in the orbit far enough that the atmosphere will decelerate it below orbital velocity.
https://what-if.xkcd.com/58/ has a good overview of the difference between suborbital and orbital velocity.