"We're normal people who can have the careers they want," said Gascon, who plays a Mexican drug lord who escapes the narco life with a sex change operation.
"Being trans in unimportant. A trans person is someone going through a transition. Once they have transitioned, that's it. They are what they are," she told the press at the film festival in southern France.
"We're first and foremost human beings, and there's no point sticking labels on us."
Gascon, 52, has written a book about having a gender affirmation operation when she was 46 when she already had an acting career, a wife and a daughter.
"On social media when you type trans, all you see is porn or insults," she said.
"I've received death threats just because I exist."
She said society had always looked for scapegoats, and targeting trans people seemed to be "the new fashion".
"Emilia Perez", a Mexico-set musical by French auteur and previous Palme d'Or winner Jacques Audiard, has dazzled the festival and received some gushing reviews.
It has earned particular praise for not fixating on the gender transition, but moving far beyond to explore themes of love, family and the victims of Mexico's gang violence.
Critics are loving the performances -- not just Gascon, but also Zoe Saldana, of "Avatar" and "Guardians of the Galaxy", who plays a frustrated lawyer enlisted by the cartel boss to help him become a woman.
There's also a surprisingly gritty turn from popstar-turned-actor Selena Gomez as the boss's unsuspecting wife and mother of his two children.
