Kevin Durant took his cold reception in Oklahoma City in stride ... clapping back at a fan's jeers ahead of his debut with the Houston Rockets -- telling the spectator, "boo you, too, motherf***er!!"
K.D. -- who played eight seasons for the Thunder -- visited the reigning NBA champs in the season-opening matchup at the Paycom Center on Tuesday ... and even though it's been nine years since he left the organization for the Golden State Warriors, at least one person in attendance wanted to make it clear they haven't forgiven him just yet.