"The proles are human beings. We are not human.” What does Winston mean in the above statement? What does it take to be “human” in your opinion?

Realization of any kind of individuality among people is what begins to change Winston's mentality from a loyal party member to a rebel wanting to do things of which the party does not approve. This epiphany is only the beginning of his desire to experience new feelings and be a new person in the context of the Party's expectation. Rebels like Winston hurt the Party when they believe that Proles are human beings; the Party does not want anyone to think this way.

The last part of your question calls for "your" opinion.