The Good Place actress, 37, blasted the attendees for having double standards for honouring a "known bigot".
On Monday, the Met Gala paid tribute to the late Chanel designer, who died in 2019, with the theme Karl Lagerfeld: A Line of Beauty.
The prestigious event attracted a series of famous faces, including the likes of Florence Pugh, Emily Ratajkowski, Michaela Coel and Janelle Monáe who have been outspoken about their pro-feminist views.
Taking to Instagram, Jamil wrote: “Last night Hollywood and fashion said the quiet part out loud when a lot of famous feminists chose to celebrate at the highest level, a man who was so publicly cruel to women, to fat people, to immigrants, and to sexual assault survivors.
“And all the women’s publications, and spectators online, chose to gleefully ignore it.
“Nobody has perfect morals, least of all me, but Jesus Christ we had a year to course correct here, and not award the highest honour possible to a known bigot.
“And everyone just decided all of a sudden we can separate the art from the artist when ‘convenient’.
“And it’s one rule for us and another rule for everybody else. Last night we relinquished our right to be taken at all seriously about anything important.”
She also pointed out the “slippery tactics and double standards”, adding: “This isn’t about cancel culture. It’s not even about Karl.
“It’s about showing how selective cancel culture is within liberal politics, in the most blatant way so far.
“It’s about showing why people don’t trust liberals. Because of slippery tactics and double standards like this.
“And it’s not just Hollywood here, the general public online participated and were entirely complicit in the erasure of the truth last night.
“They replaced their pitchforks with spoons last night, to lap that s**t right up… If we carry on like this, don’t be shocked when we lose the next election.”
This isn’t the first time the star has criticised the decision to honour the designer, who died in February 2019, at the Met Gala.
After the theme was announced, she shared a series of screenshots highlighting his controversial comments.
She captioned her post: “Why is THIS who we celebrate when there are so many AMAZING designers out there who aren’t bigoted white men? What happened to everyone’s principles and ‘advocacy’.”
“You don’t get to stand for justice in these areas, and then attend the celebration of someone who revelled in his own public disdain for marginalised people.
“Sorry, but no. This isn’t the Nineties. We didn’t fight all this s**t just to throw it all away because some white guy made some pretty clothes for people’s skinny faves… come on now.”
Lagerfeld made a slew of controversial opinions about a string of issues, including the MeToo Movement, migrants, LGBTQ+ rights and women’s bodies.
When asked in 2012 by Channel 4 whether he should stop hiring models who looked unhealthy, the German designer said: “There are less than one percent of anorexic girls.
“But there are zero in France, I don’t know in England — over 30 per cent of girls [are] big, big, overweight and that is much more dangerous and very bad for health.
“So I think today, with the junk food in front of TV, it’s something dangerous for the health of the girl. The models are skinny, but they’re not that skinny.”
He claimed a year later, on an episode of Le Grand 8 on French television that “the hole in social security, it’s also [due to] all the diseases caught by people who are too fat” and that “no one wants to see curvy women on the runway”.