3 false or questionable assumptions that individuals often make (about anything)

What makes these assumptions false or questionable?
Which false or questionable conclusions might one very easily draw from each of these assumptions?
What makes these conclusions false or questionable?

Suppose in a grocery store, you see a man dressed in old and dirty clothes, with long, shaggy hair. You might conclude that he's a street person who may want to shoplift.

Take this assumption from there.