In fact I don't see differences of opinion in a wholly negative light, and again, I think this idea that we are celebrating difference is actually the opposite of what really occurs.
I suggest that the development of differences in isolation is deeply negative. Imagine if scientists would regularly refrain from discussing their various different experimental apparatuses and theoretical models because they believed one to be better than the others. It would lead to a deep stagnation of science. If we want socialism to develop a science of transformation, then our theories and approaches are going to have to be hashed out not just in isolation, but in conversation and comparison. This can't happen with the current ultra-sectarian attitudes that people promote. Instead you get ossified orthodoxy. If anything has failed spectacularly and for a long time, it has been the extreme sectarianism of the left.