Most vegetarians I ever see looked enough like their food to be classified as cannibals.

The line is a barbed, comic inversion: instead of vegetarians resembling the moral purity often associated with abstaining from meat, they are said to resemble vegetables so strongly that eating “their food” would amount to cannibalism. The humor depends on exaggeration and category confusion—treating “looking like vegetables” as a literal identity rather than a metaphor for pallor, thinness, or perceived frailty. It also reflects a common strain of turn-of-the-century American satire that mocked dietary reform movements and fads by portraying adherents as physically unappealing or self-denying to the point of absurdity.