When someone says there are only two choices, the fools are sincere and the liars have hidden the third. The quickest way to identify a fanatic is to see if they think those who are not for them are against them, or those who are not against them are for them. Both versions appear in the gospels, but they represent opposing worldviews. In the first, the world is filled with enemies, in the second, allies.
I bump into binarians most often when I talk about Tibet: supporters of the Dalai Lama think you're either for them or China. This is like saying that in World War II, either you were for Hitler or Stalin—the two biggest players are rarely the only choices.
The hard part of rejecting binarianism is binarians may unite against you. When Protestants and Catholics were happily massacring each other, they both hunted the unitarian, Michael Servetus, to burn him for heresy. (The Protestants won that one.)
The price of free thought is the hatred of people who do not want anyone to be free.
For more about the either-or fallacy: False dilemma - Wikipedia.
* If this was a post from Brother Will, he would say that the Gospel of Matthew's "Those who are not for us are against us" might've been a mistranslation, or it might've been an early stage in Jesus's thought, or it might've been what persecuted Christians believed Jesus said. The mature sage's teaching is in the Gospels of Mark and Luke: "Those who are not against us are for us."