It is up to the writer to take whatever approach he wants with the essay. He can be argumentative or agreeable while writing the views and opinions.
It is not always necessary to express personal or people's opinion in the essay, it may simply explain and event in detail as well.
Before writing an expository essay, it is important for the writer to analyze study and review the subject thoroughly so that he can analyze it from all aspects. And it should be the writer’s objective to select the best words for expressing the idea so that the message is clear.