If you will notice, the main issue with doping in cycling isn't necessarily power. It is a drug which makes the body produce more red blood cells which increases the athletes ability to carry oxygen. The more oxygen, the more endurance. The problem is that over time, there are so many red blood cells that the blood turns to syrup and heart can no long pump it efficiently and you drop dead of a heart attack. Some of these super tuned athletes have resting heart rates in the teens. Not really good when you're trying to pump 50W blood!
Anyway, the pressure is always there to perform and get results for your sponsers. The racers who were barred, are not yet guilty of doping. They have only been associated with a doping doctor, as was Lance at one time. IMO, it is much better to barr them now, before the race, and let the race be as clean (no pun intended) as possible. I would think that not one of these guys would want to win the Tour De France because the 1st place guy got thrown out for doping. Please remember that this sport is very cut throat and I wouldn't count out the chance of a conspiracy.
Go George!