People often have conversations in which we label others into groups. Those group identities can be created by others or the group themselves. Either case, when we talk about the group ambiguity creeps in. The perceiver may make the assumption that the conversation must apply to the entire group rather than the group in general. This is a fallacy I will call the Assumed All Fallacy.
For example, if I were to make the statement, “The English love to tea,” it would be a fallacy to conclude that there is an “assumed all” in the statement. It is probably that there are at least a few English who do not in fact love tea. The statement about English loving tea is a general statement.
Loving tea is not in this case a defining characteristic of being English and so therefore it should be interpreted as a general statement about many or most English rather than “assumed all” statement about every single man and woman living in England.
Now, let’s take this fallacy into a more controversial application. “Christians oppose same-sex marriage.” This again is a general statement and not a statement about every single Christian. To assume that this statement refers to every single Christian and not to Christians in general would be an example of the Assumed All Fallacy.
“Muslims use fear and terrorism to suppress criticism.” Again, this statement is not a defining characteristic of all Muslims; it is a general statement about many Muslims. In fact, it has become such a common characteristic that the Muslim culture has become known throughout the world for this tactic. Obviously there are Muslims who do not use fear and terrorism to suppress criticism just as there are English people who do not like tea. But the statement in general is true. When people “assume all” in such statements they are being fallacious.