Jerry,

The signature is a generalization. Get it? Intended to be a joke.

If I had stated "All generalizations are true", it wouldn't have been funny.

From Merriam-Webster online: (bolding and colors are theirs)

Main Entry:1joke Pronunciation: \ˈjōk\ Function:noun Etymology:Latin jocus; perhaps akin to Old High German gehan to say, Sanskrit yācati he asksDate:1670 1 a: something said or done to provoke laughter; especially : a brief oral narrative with a climactic humorous twist b (1): the humorous or ridiculous element in something (2): an instance of jesting : kidding <can't take a joke> c: practical joke d: laughingstock2: something not to be taken seriously : a trifling matter <consider his skiing a joke — Harold Callender> —often used in negative constructions <it is no joke to be lost in the desert>


Also from M-W online:

Main Entry:gen·er·al·ize Pronunciation: \ˈjen-rə-ˌlīz, ˈje-nə-\ Function:verb Inflected Form(s):gen·er·al·ized; gen·er·al·iz·ingDate:circa 1751 transitive verb1: to give a general form to2 a: to derive or induce (a general conception or principle) from particulars b: to draw a general conclusion from3: to give general applicability to <generalize a law>; also : to make indefiniteintransitive verb1: to form generalizations; also : to make vague or indefinite statements2: to spread or extend throughout the body
— gen·er·al·iz·abil·i·ty \ˌjen-rə-ˌlī-zə-ˈbi-lə-tē, ˌje-nə-\ noun
— gen·er·al·iz·able \-ˌlī-zə-bəl\ adjective
— gen·er·al·iz·er noun


And:
Main Entry:1false Pronunciation: \ˈfȯls\ Function:adjective Inflected Form(s):fals·er; fals·estEtymology:Middle English fals, faus, from Anglo-French & Latin; Anglo-French, from Latin falsus, from past participle of fallere to deceiveDate:12th century 1: not genuine <false documents> <false teeth>2 a: intentionally untrue <false testimony> b: adjusted or made so as to deceive <false scales> <a trunk with a false bottom> c: intended or tending to mislead <a false promise>3: not true <false concepts>4 a: not faithful or loyal : treacherous <a false friend> b: lacking naturalness or sincerity <false sympathy>5 a: not essential or permanent —used of parts of a structure that are temporary or supplemental b: fitting over a main part to strengthen it, to protect it, or to disguise its appearance <a false ceiling>6: inaccurate in pitch <a false note>7 a: based on mistaken ideas <false pride> b: inconsistent with the facts <a false position> <a false sense of security>8: threateningly sudden or deceptive <don't make any false moves>

This would probably be known as "taking a joke too far".

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The apostrophe troll.