Stealth Rock is the one questioned because both Spikes and Toxic Spikes can be avoided by simply the typing of the Pokemon. True, they can be "unfair" entry hazards, but Stealth Rock hits every Pokemon in the game. Both Spikes and Toxic Spikes can be avoided by Pokemon that either fly or levitate. Also Toxic Spikes can be completely absorbed and rendered useless if a Poison type is sent in. Stealth Rock only needs one turn to be used for full effectiveness while Spikes and Toxic Spikes, although useful without all those layers, aren't completely effective in one turn. I can see the reason to why Stealth Rock is questioned. Nevertheless, it shouldn't be banned at all.
Competitive play is all about strategy. You use what's available to you. Anyone can decide to incorporate Stealth Rock into their team so I don't see why it should be banned. Taken into factor the Pokemon who move ranks because of the 50% Health reduction...well that's just how the mechanics work. Take advantage of it or not...Stealth Rock is a utility. Use it or not, it's always going to be there. Needless to say...Rapid Spin solves all of your problems xP (not being serious of course but you know).
As for Rapid Spin being the only thing that can clear entry hazards on your side and it being a normal type which doesn't work against ghosts...well you have to incorporate that into your strategy as well. =P
On a random note I find the move Defog hilarious...your opponent can always use that on you in a merciful way.