The GoDaddy.com CEO who shot and killed an African elephant is now taking aim at PETA for blasting his hunting trip -- vowing he won't be extorted by the animal defenders.

Bob Parsons triggered controversy after posting an Internet video chronicling his elephant slaying during a trip to Zimbabwe.

TMZ obtained a copy of the letter PETA sent Parsons, presenting him with its "first-ever Scummiest CEO of the Year Award" -- and informing him PETA is "taking our domain-name business elsewhere."

Parsons tells TMZ, "I understand PETA has an agenda, but I refuse to go along with their extortion-style practice."

Parsons claims he was only hunting "problem elephants" -- ones that destroy the villagers' crops ... adding, "I stand by my decision to help African villagers." Parson claims he has the support of tribal leaders there.