Did Zoro Really Say “Only I Can Call My Dream Stupid”?

Yes. Roronoa Zoro says "only I can call my dream stupid" in episode 24 of One Piece, during the Baratie arc, and he says it to Sanji. The wording on the poster is the dub's, the scene is where the sources say it is, and the line means on a wall roughly what it means on screen, which for a Zoro quote is rarer than it should be.

The verdict

True. CBR's ranked list of Zoro's lines places it in the Baratie arc, episode 24, "Hawk-Eyes Mihawk! Swordsman Zoro Falls into the Sea!", and Screen Rant's feature on the lines that show Zoro will become the greatest swordsman describes the same exchange: Sanji mocks the crew's dreams, and Zoro answers that the right to call his dream stupid is his alone. The two publications are one newsroom, which this site counts as a single source, but the episode is not in doubt; it is the one in which Zoro loses to Mihawk and makes the vow about scars on his back that Wikiquote records under the same episode number.

The scene the poster leaves out

The line comes before the fight, not after. Zoro says it while the crew is still bantering in a restaurant, hours before the greatest swordsman in the world opens his chest with a knife, and its placement is the joke and the point. He claims his dream as his own to mock, and then the episode makes it look stupid in front of everyone: he loses, badly, to a man who barely tries. The vow he makes afterwards, bleeding in the water, is the same claim restated with the stupidity conceded. Only he can call the dream stupid; he has just found out exactly how stupid it is; he keeps it anyway. Quoted alone the line is defiance. In the episode it is the setup for the most humbling scene the character ever gets.

Why this one is real when others are not

Zoro is the One Piece character most often given lines he never said, because his laconic register makes any terse imperative sound like him; this database has already had to sort out his name, and a widely shared line about the world shoving you around was checked for this page and left unpublished because no trusted source can place it. This one is different. It is short, it is in the dub, it is in the editorial record with an episode, and it belongs to a scene everyone remembers. The verified Zoro lines on this site, on his page, are the ones that cleared the same bar.

How we checked

The verification process asks for a primary or editorial source; the editorial record gives the episode and the exchange, and Wikiquote's transcript of the same episode confirms the scene even though it happens not to transcribe this line. The entry in the fact-check database is true, and the rest of the crew is on the One Piece hub.