People are divided because we have different opinions, values, beliefs, worldviews, motives, personalities etc. We're also a social species so we form groups that tend to share some of those characteristics. Those divisions are inevitable and without them we wouldn't be fully human. Division is therefore neither good nor bad, it's simply part of being human and it will always exist.
People are unified because we often share all of the above with others. That's inevitable and without it we wouldn't be fully human. Unity is therefore also neither good nor bad. It's equally a normal and healthy part of being human. Unifying language has been used to impose totalitarian regimes throughout the 20th century, on all sides of the political spectrum. Unifying language can be used to suppress individuality and enforce conformity with a majority or with authority. A world without division would be a world of lifeless clones.
Language expresses unities and divisions that already exist and therefore allows us to try to find appropriate balances between the two through self-expression and communication. Divisive language should therefore not be censored any more than unifying language should be.