If Gamora, Star-Lord, Drax, Groot and Rocket were called the Gardens of the Galaxy, they wouldn’t be saving aliens from harm, they’d be a business specializing in lawn and plant upkeep.
For God’s sake, Nebula is joining the team in this movie, and while mockingly talking to Gamora, she sincerely calls her a “Garden” of the Galaxy.
Even though Drax’s “stupid” reply obviously comes from a different part of the movie, it was a nicely cut to make Nebula’s mistake look even worse.
It's Showtime - Marvel Studios' Guardians of the Galaxy Vol. 2 Preview