One of the contradictions of course was the fact that Trotsky and the "left" opposition supported collectivization. as opposed to the Bukharinists. In fact a lot of the left oppositions plans were adopted in a very distorted way by the Stalinist bureaucracy in the late 20s leading a fairly large portion of the opposition to see reconiliation with Moscow. The famine of course was used as a political tool by Stalin... and collectivization would have been handled in an entirely different way if Trotsky was in power-- that's indisputable.