Actually, the Department of Homeland Security has trademarked the slogan, so it is displayed as "If you see something, say somethingTM." Which may mean the U.S. government is encouraging its citizens and noncitizens alike to practice Transcendental Meditation (which is a proprietary name and is followed by a TM; maybe even TM TM, for an abbreviation followed by a trademark declaration).
If you see something, say something.
If you see injustice (verbal, physical, social, economic), say it is wrong.
If you see justice, say it is right.
If you see lies (in print, on TV, online), say something truthful.
If you see intolerance, say something tolerant.
If you see error, say something factual.
If you see something banal, say something provocative.
If you see something grammatically naked, say something syntactically dressed up with every place to go, with gerunds, participles, prepositions, ablative absolutes, infinitives, adjectives, adverbs, articles, conjunctions, auxiliary verbs, pronouns, synonymous nouns, and parenthetical asides.
If you don't see something, don't say something.
If you don't see anything, say anything but nothing.
If you see some things but not others, say something to yourself to discern why.
If you see nothing, say nothing. (But say it eloquently.)