Why did the French Canadians not want confederation?

The main reason why the French Canadians (but not only them) were opposed to the Confederation is that the central government would not consider their wishes - so in other words, that they would be overruled by the central government

(they were already in an Union with English speaking population, so that wasn't the main problem).

The French Canadians did not want confederation because they believed that the idea of having one central government is bad for the provinces. They believed that if Confederation occurred, the provinces will lose their power and the french might lose their rights and language.