Oligopoly is a concept in economics where several firms sell almost identical products and keep out competition. They are not motivated to improve their products or cut prices because they find themselves in very comfortable circumstances, dividing up the spoils.
The aluminum, steel and cement industries once were oligopolies. These industries tried not to differentiate their products from each other or charge lower prices than competitors.
The problem for all of them turned out to be someone else was able to produce what the oligopolists thought no one else could do. Both foreign and domestic producers came up with better products and lower prices.
Some established mainline Christian denominations think and operate like industrial oligopolists. They think it is harmful to all to bad mouth each other. Instead, they have ecumenical conferences and heap praise upon each other.
If a denomination is not confident of its theology, it may serve its purpose to make peace with others in the oligopoly so as to not be forced to defend itself. If, however, one denomination believes it has something better to sell, a better truth, it would be in its interests to point out the shortcomings of others.
If they do not do this, the shortcomings of others will attract competitors. These competitors, like atheists, may take business away from all.
Unfortunately, some like the author attached, believe denominations should huddle together like the oligopolies of old. The no nothing white self rightous condemation preacher has come to represent all of Christianity.