Why did French Canadians dub Slap Shot in Canadian Quebec French instead of Canadian French?

According to doublage.qc.ca, the official canadian dubbing website:

This movie has been dubbed in Joual, a particular from of French Canadian language.

Here is an article I will try to translate the best I can:

Québec is facinated by the movie Slap Shot, released in 1977. ( . . . ) The translation in Canadian Quebec french was historical.

It was the first time an american movie was translated in our words, in québécois.
( . . . )
When Slap Shot was introduced in France, it was in a typically french version who did not convinced the writer Nancy Dowd. When Universal Pictures delegated the dubbig to Hubert Fielden, a French living in Quebec, he decided to do it in québécois without censoring anything. This ended with all the famous quotes that we all know by heart.

Here is an interview of Hubert Fielden where he says:

I told them it would be better in "québécois"! They asked me if I could adapt the dubbing and I said "Yes, I can!". It was the first time we dubbed a movie in "québécois" here.
( . . . )
Dubbers from Quebec were used to dub in international french, so at the beginning, it was more difficult.

I'll try to answer this question since I'm a French-Canadian. I'll start about the French-Canadian thing. BTW @Steve-O, nice comment dude :) North America started with the natives then came others like Basques, Vikings, etc.. And Columbus arrived south. The first to really establish a stable foreign community were the French followed by the Brits who mainly established themselves in today's USA then in Canada. Brits eventually got over the way smaller French community but were never been able to subdue them. Brits also got in trouble with the now North American Brits who kicked their arses (Yay!).

So everything really started in Quebec when it comes to North America and the Quebecers managed to stand strong and keep their identity through the ages. @Steve-O Described the situation: there's is French-Canadians only and that's it. However French people are spread all over Canada, BUT mainly in Quebec. Funny thing is that Canada is supposed to be a biligual country, Quebec is the main province when it comes to French language, but New-Brunswick is the only province being officially bilingual! LOL

This being said, Hockey is a religion in Canada and even more in Quebec. Montreal Canadians are among the 6 original NHL team and a vast majority of Canadians have played hockey at one point in their life and push the bar even higher when it comes to Quebecers.

Now, about Slap Shot. This movie is about the infamous East Coast League, a league for wannabe NHL players and Goons (so it was in those days). Slap Shot is a parody of the ECL. The Henson brothers really existed but their real name is Benson and they were two, not three. Now, imagine this movie using a real purified language, very far from the crude harsh one in reality. It'd be laughable, and not in the good sense. Also imagine a movie about Cow-Boys from Texas but with a New York accent... I know, My God... :)

The translation for French-Canada was made with the real low class French-Canadian words, just like they used the real low class American English words to stick to the reality. And to me it's what makes this movie so good and a classic among sports fan. The true language used and we all laugh at that today. As for the French, for France, language... Oh boy.... Imagine a classic North American English movie in stuck-up-Brits-language... That's what is Slap Shot in the purified and stuck-up French from France language.

Bottom line, Slap Shot in French-Canadian is good because it kept the true coarse language. The version in French for France sounds like a western movie with cow-boys from Texas with a purified and stuck-up new York accent from the upper class easily offended by words. You know what I mean :)