Accident

We often arrive at a generalization but don't or can't list all the exceptions. When we reason with the generalization as if it has no exceptions, we commit the fallacy of accident. This fallacy is sometimes called the fallacy of sweeping generalization.

Example:

People should keep their promises, right? I loaned Dwayne my knife, and he said he'd return it. Now he is refusing to give it back, but I need it right now to slash up my neighbors' families. Dwayne isn't doing right by me.

People should keep their promises, but there are exceptions as in this case of the psychopath who wants Dwayne to keep his promise to return the knife.