Aim assist is part of almost all console shooters. With the sloppiness of trying to be really precise with a thumbstick, it's practically a necessity. If you want to prevent silly moments where two perfectly capable and seasoned players spend three clips of ammo shooting back and forth to finally get a kill, because they happen to both just be barely missing each other due to minor sloppiness.
What's the alternative?
If they take out the aim assist, players scream, "OMG, the controls in this game are so sloppy you can't hit a thing!"
If they broaden the hit box around the player so that close shots still count, players scream "BULLS#!T".