The accusations fly from the Lorax's lips. The Once-ler, he says, is "crazy with greed" (110). Then he disses the Thneed, arguing that nobody will ever buy it.
(We have to admit, we're kind of tempted by the fuzziness and color choices of the Thneed. And, of course, the whole butterfly milk scent.)
Bad timing. Right after the Lorax tells the Once-ler that nobody needs a Thneed, somebody comes up and buys one for just under four bucks. Hmmm.
The Once-ler laughs at the Lorax, who reminds him that it's he who speaks for the trees. (In case you'd forgotten.)
Obviously, this isn't swaying the Once-ler. He tells the Lorax to get lost.