It wasn't a Lorax fandom so much as a Once-ler fandom: http://knowyourmeme.com/memes/once-ler

"Once-luts

A darker side to the fandom exists, just as with many other fandoms, which focus strongly on sexual imagery, fan-fics and role-play and slashing characters from the movie. The main attraction in this category is a theme called “Oncest” in which the “nice” Once-ler is paired up with an evil version of himself. Several blogs are dedicated solely to Once-ler smut and sexual imagery – often taken to ridicules levels, including pancake batter, marshmallows and thneed-bondage."

I see, give the Once-Ler a Bieber cut and the Twilight demographic falls in love with him.

Here's a brilliant retro rendition of the Once-ler as a reader might have imagined him before the movie - http://knowyourmeme.com/photos/294355-Once-ler - a severly misguided corporate douchebag who genuinely thinks that what he's doing is the best possible option. The 1972 special (which I've reuploaded in one-video form to http://www.poetv.com/video.php?vid=42487 ) expands on the original in the best possible way by building on the original book's intentional ambiguity - the Once-ler asks the Lorax what the hell all his employees will do if if he shuts down his factory, and at one point debates with himself, concluding that if he doesn't sacrifice the environment, somebody else probably will.

The comparison to bronies on that page was pretty apt.