The letter attacks feminist social media campaigns like #Metoo and its French equivalent #Balancetonporc (Call out your pig) for unleashing a "puritanical ... wave of purification".
The letter has receeived a mostly hostile reception on social media, quickly becoming the most tweeted story on Twitter in France.
And a group of feminists on Wednesday hit back with an accusation that the letter's signatories of having "contempt" for the victims of sexual harassement.
"As soon as there is progress in equality, even by a millimetre, well-meaning folk immediately warn us of the danger of going to extremes," they say in another open letter published by francetvinfo.
The signatories of the original letter, published in the daily Le Monde, claim they are defending sexual freedom, for which "the liberty to seduce and importune is essential".
The letter claims that "legitimate and necessary protest against the sexual violence that women are subject to, particularly in their professional lives" has turned into a witch-hunt.
"Rape is a crime, but trying to seduce someone, even persistently or cack-handedly, is not -- nor is being gentlemanly a macho attack," says the letter.
Oscar-nominated French actress Catherine Deneuve declared Tuesday that men should be "free to hit on" women and has previously expressed annoyance with the #Metoo social media campaign.
"Instead of helping women, this frenzy to send [male chauvinist] 'pigs' to the abattoir actually helps the enemies of sexual liberty -- religious extremists and the worst sort of reactionaries," the letter says.
It goes on to claim that the #Metoo campaign is in danger of stirring up "hatred of men and of sexuality."
Women are "sufficiently aware that the sexual urge is by its nature wild and aggressive", it declares. "But we are also clear-eyed enough not to confuse an awkward attempt to pick someone up with a sexual attack."
It also deplores men being forced into "public confessions ... and having to rack their brains and apologise for 'inappropriate behaviour' that might have happened 10, 20 or 30 years before" and claims that a "puritan wave" is already bringing censorship in its wake.