From a talk by the Rebbe on 12 Tammuz, 5737 – June 28, 1977:
There is a school of thought that in order to bring close “alienated” Jews we must go to them with an abridged and reformed version of Torah. But others have tried this approach before them.
Although we’ve already seen where the compromises lead – that they not only do not bring close those who are far from their heritage, but they actually drive away those who are close – the evil inclination is again raising a tumult that this is the way to save Jewish youth. So they try new experiments, on living Jewish souls and living Jewish bodies!
The problem stems from the philosophy that the Jewish people are like all other nations – they must emulate gentile values and lifestyles, instead of themselves being a light unto these nations.