"He (Lévesque) said a society is judged partly by the way it treats its minorities," Couillard told a news conference in Quebec City.
"I think the days of open nationalism in this political party in power are over."
Couillard urged the government to drop the proposal to ban the wearing of conspicuous religious symbols.
Polls have suggested a majority of Quebecers support restricting minority accommodations. However, other polls suggest voters in the province place the issue relatively low on the list of political topics they care about.
The government says its so-called secularism charter will be the subject of public consultations, then presented as a bill to the legislature this fall.
Some members of religious minority groups have promised to fight the plan or leave Quebec, as the mayor of Calgary and government of Ontario have invited them to do with the promise they'd be welcomed with open arms there.
Scores of mostly Montreal personalities have also signed an open letter slamming the plan.
The mayors of all 15 municipalities on the island of Montreal have issued a joint statement against the charter, asking the government to deal with more pressing issues such as crumbling infrastructure and the stagnant economy.
Protest planned against charter
Adil Charkaoui, a spokesman for the Quebec Collective Against Islamophobia, said Wednesday that several thousand people have already indicated on Facebook they will join the demonstration against the government's plan on Saturday.
He said he expects about 20,000 people to take part, including members of the Muslim, Sikh and Jewish communities as well as nurses, teachers and daycare workers.
"It will be a family protest," Charkaoui said. "And we are sure that we are going to send a very strong message to Madame Marois that she cannot force people to forget their roots, their religion, their beliefs."
Charkaoui, a 40-year-old father of four, was arrested in 2003 and accused by Ottawa of being a terrorist. In 2009, a security certificate against the Moroccan-born Montrealer was declared null and void.
Charkaoui spent more than six years under suspicion of being an al-Qaida sleeper agent, spent 21 months in jail and had to wear an electronic GPS-bracelet.
The charter does have its supporters — including within minority groups. One group, comprising small-l liberal North African Arabs, expressed support for a secularism plan even before it was tabled.
Akli Ourdja is an Algerian immigrant living in Montreal who is part of a group called The Quebec Association of North Africans for Secularism.
He says his native country fought a civil war because of religious extremism, and he doesn't want to see that here.
"I feared for my daughter," said Ourdja.
Ourdja said he believes his daughter might be influenced to wear a hijab if she had a teacher at school who wore one, and the best way to protect her is to prevent teachers from wearing them.Suggest a correction