It is a non issue for Steam, as such they have no ground to remove the game from users library.
Nothing ruins future sales like lack of demand due to past sales.
That said, it's done all the time via apt-get or windows update or other program updates. People think that this rises to a new level though, and given the fact that Steam users are younger, tech-saavy, and more vocal it's no wonder that it's raising a stink.