Those Typo Eradication guys needed this advice from Miss Manners--which oddly enough cameon Wednesday, August 20, two days before the news hit about the sentencing of the Eradicators.
(Miss Manners writes for the Washington Post; s'pose she knew they were on trial?)
. . . neither of us can run around insulting people, which is what an amazing number of people do when they detect errors, little thinking that they are committing worse errors in so doing.
This applies to correcting individuals, however, not institutions. So you may inform those in authority to act (which the salesperson you approached probably was not) on mistakes of which you sympathetically know they would want to be aware.