A sweeping generalization applies a general statement too broadly. If one takes a general rule, and applies it to a case to which, due to the specific features of the case, the rule does not apply, then one commits the sweeping generalization fallacy. This fallacy is the reverse of a hasty generalization, which infers a general rule from a specific case.
Example
(1) Children should be seen and not heard.
(2) Little Wolfgang Amadeus is a child.
Therefore:
(3) Little Wolfgang Amadeus shouldn’t be heard.
No matter what you think of the general principle that children should be seen and not heard, a child prodigy pianist about to perform is worth listening to; the general principle doesn’t apply.