The poet laureate and activist recently joined forces with MilkPEP -- a marketing arm of the dairy industry that created the famous "Got Milk?" ads -- to advertise the inaugural Every Woman’s Marathon, that's touted as "the only U.S. marathon designed for women, by women."

MilkPEP and Gorman released an ad where she recites a poem over different images of women running and training. Check out the vid -- it's a catchy poem and a pretty inspiring message.

But, not everyone's giving it two udders up. PETA's written a letter to Amanda questioning why she would support an event put on by MilkPEP ... essentially, in the org's eye, cosigning the dairy industry's alleged mistreatment of animals.

Lisa Lange, the animal rights group's senior VP of communications and distance runner, wrote the letter and expressed confusion at Gorman's partnership ... adding she'd "no more drink cow's milk at the end of a race than I would smoke a cigarette."

LL says any woman who participates in the event is a sucker, falling for a trick by the dairy industry -- which she accuses of destroying the environment, causing the cows physical and emotional distress and making a large part of the American population sick, due to lactose intolerance.

In the letter, PETA calls for Gorman to back out of the event, saying the "voice of a generation" must see "exploitation" of a female of any species -- bovine or human -- as wrong.

FWIW ... Gorman's supported animal rights causes in the past, even encouraging others to rescue animals from shelters after her beloved dog of almost 20 years died a few months ago.

As much as PETA agrees with her on that issue -- they're clearly not on the same page where this marathon's concerned. Not even close.