Shared language is a myth. Having a shared language would require a shared reality. By this, I mean that people would be required to have a multitude of shared experiences before effective communication would be possible. In the past, I believe that this was accomplished through shared literature/media, a shared culture, a shared religion, shared civic institutions and experiences within those institutions, and further through doing things with one another. Simply spending time together, and going through life together can accomplish this to some extent (provided that the people are communicating honestly and are emotionally available, willing to share deeper and more intimate beliefs and personal history).
Gaining shared language is impossible if people are unwilling to invest the time and emotion to achieve the goal. Why? Well, words and phrases are loaded with contextual meaning and emotion for every individual. For a person of my age, one's "background" would mean work history, family of origin, culture of origin, the environment in which one was raised, religious history, and still more. It would involve even the character of the relationships one had. For the younger members of my generation (millennial), this changed merely to socio-economic status and takes a flavor from intersectionality. This is further complicated by the fact that the word "intersectionality" is largely foreign to older members of the millennial generation, and almost completely unknown to gen-x-ers and boomers. A single word like "background" can have two radically different meanings within a single generation of Americans. How then does a society perpetuate if communication cannot be had, if a shared language is non-existent?
Looking at the current far-right/alt-right and the far-left/antifa, one would assume that these individuals simply cannot co-exist under one vaguely democratic government. It would seem that they are doomed to fight and tear the country apart. Yet, these two groups are playing identity politics, believe in a strong central government, believe in legislating morality, and believe quite strongly that social status and class are enforced by the state to some extent. The differences are in where and how they draw the divide. The far-left views history as a class struggle (hence the term cultural Marxism) between cis, straight, white males and all other members of society. The more deviant from the norm one's identity may be the more oppressed and therefore laudable that individual would be. The more common one's identity the more obloquy one suffers. To the far-right, history is the maintenance of "Western culture" and identity, where-in all are expected to conform to a standard set by the majority (white anglo-saxon protestants). They see history as a struggle of "their kind of people" to exist and perpetuate against a leftist agenda to eradicate their way of life. To them, the more material success and the more life satisfaction that one can attain the more lauded the individual. The less one achieves in either front the more obloquy that person will suffer. In this sense, both appear to have (what they believe to be) an objective world view that exists at odds with the other.
Are they truly at odds? If we assume that they are viewing things in either a classist or racist framework, then yes. If the alt-right were truly classist with racial bigotry and misogyny entering in due to bell-curve styled thinking, and if the far-left were truly classist and racist in the opposing direction, then yes. They would be absolutely at odds. I would argue that this is not the case for either group.
From what I can see of the alt-right, much of their beliefs are reactionary to a left that has called for their destruction. From what I see of the far-left, much of their beliefs are reactionary to a right that has refused to acknowledge the struggles of the marginalized. This would logically follow from a majoritarian society. The truth is that both sides are willing to accept people of any stripe so long as those individuals are likewise willing to accept them. The breakdown is, as far as I can discern, that neither group can communicate anything to other due to a lack of a shared reality. There are no similarities in the lives of the individuals on either side, and even where similarity exists the mind that perceives those realities colors every perception with language and further dissimilar experiences.
Within a civilization that is at once multicultural, individualist, majoritarian, and maintaining a pace of change in which an age gap of just five years can result in different technologies, variant living standards, entirely dissimilar media, and bewilderingly different education, how can one expect anything other than political tensions that threaten to tear that civilization apart?
Effective communication can breed understanding and unity, but that selfsame communication requires a context. It requires a shared reality that is sadly non-existent. No context for communication exists in human civilization at this point in time, if ever it did.