Please note that when the Left is out of power, they never unify around other groups' agendas. "Unity" always means unifying around the Left's agenda -- as in Washington, "bipartisan" always means doing what Democrats propose, never what Republicans propose. When the Left is out of power, "dissent is the highest form of patriotism," but as soon as they achieve power, they marginalize all those who threaten the "unity" they say is so important.
Well, here's a thought. I do not believe that unity is a precondition of social or political or religious achievement -- and only scoundrels will tell you it is. Rather, unity is the result of social or political or religious achievement -- after all the hard work has been done to hammer out a plan of action and to achieve consensus around it.
It follows that "unity" is not, in and of itself, the sine qua non of group life. A nation or a party or a religious body which values "unity" over real agreement on its nature, values, or course of action is a fraud and cannot advance. In the absence of real advancement, though, mere control -- the exercise of raw power -- may be achieved, and should be resisted.