I agree that he should sit out the Tour. He screwed up, he's taking responsibility and accepts that decision. They probably should take his driver's license away as well while we're at it.
He made an error in judgement using drugs. Haven't we all made stupid mistakes? And some of us have paid for those msitakes dearly. But does that mean we should crucify him and make him an outcast? Or is that part of the problem? When people need their friends the most they get isolated and lose that support system. Isn't that opposite of what should be done?
So I have no problem with the Quick Step team standing behind their rider. I'd do the same if my friend or teammate made a mistake.
I still beleive he should be punished but I don't agree that he should be kicked off his team. Like Merckxx I believe in second chances. But make it clear that if he does it again he will be kicked off the team for good.