Let's say a monster tries to slide Player X through Player Y's square. Player Y will naturally object to this; she doesn't want her ally moved through her square to a disadvantageous location! If I go by the RAW, then I have to tell her she can't stop it, and either come up with some shaky in-game justification or simply resort to "them's the rules"--both of which I feel are disruptive to immersion.
But then again... you can also have the situation where the Large or Huge monster with the oversized greatclub swings and connects with Player X and and hits him so hard he gets to slide Player X three squares as the player flies across the room. Why or how can Player Y stop this from occuring, even if Player X goes flying right next to him? If anything... if we're talking immersion here... if Player Y tries to stop Players X by getting in his way... Player X should just as easily get slammed INTO Player Y... thereby sending both of them tumbling three squares. That's just as valid a rules interpretation if we're using the "reality" and "physics" of the situation in order to justify the game mechanics.
Obviously the immersion reasoning affects people in many different ways, and what bothers one person doesn't affect another in the slightest... but this is exactly why I don't bother trying to use real-world science or physics to explain, change or justify why the game mechanics do things a certain way. There's always another case where using the real-world to justify game rules just breaks things down.