[the phantom]

Yes, the pilgrimage of the Noldor to ME resulted in many good things, the improving of mankind being one of them. Also, the rest of ME was for the most part protected from Morgoth while he was busy with the Noldor. Third, the Noldor weakened Melkor by keeping him in a constant state of war. He spent himself a lot during this time, which made his overthrow less apocalyptic when the Valar came against him.

So it seems that the Noldor coming to ME was a very positive thing. But why was their coming to ME a "rebellion" and "evil". It was only a rebellion because the powers (Valar) were against it. If the Valar wouldn't have been so dead set against them leaving the kin slaying wouldn't have happened. The reason stated as to why the Teleri would not help the Noldor reach ME was it was against the will of the Valar. If the Valar wouldn't have hindered the Noldor by condemning them and asserting their influence over the Teleri to not help them, the flight of the Noldor would not have been an evil thing.