Overview
The package-deal fallacy (also known as false conjunction) is the logical fallacy of assuming that things often grouped together by tradition or culture must always be grouped that way. False conjunction refers to misuse of the and operator.
It is particularly common in political arguments, such as the following imagined example from the United States: "My opponent is a conservative who voted against higher taxes and welfare, therefore he will also oppose gun control and abortion." While those four positions are often grouped together as "conservative" in United States politics, a person may believe in one "conservative" idea while not believing in another.
Additional examples
"John likes surprises, so he'll enjoy finding a snake in his sleeping bag."
Assumes a surprise is inherently a good thing does not consider the actual context of an event.
"Droughts are common during summers in Country X, so water is hard to find there in August."
It hasn't rained in Country X for a while, but there may well be plenty of water reserves available. Also, seasons are different between the two hemispheres; if Country X is in the southern hemisphere, August will be in winter. Lastly, just because droughts are common in summer in country X does not mean they must occur every summer. That August may have been one of the summers a drought did not occur.
"A child molester was caught in a nearby neighborhood. He was friends with many of his neighbors. Everyone in that whole neighborhood is sick."
Assumes that the neighbors knew that their friend was a sex offender and implies their endorsement of such activity. Assumes guilt by association under incidental circumstances.
When it is not a fallacy
From Wikipedia (CC BY-SA 4.0).