I have a similar experience, but my impression is that Parisians have little patience for accents in general. People elsewhere in France where I've visited (Aix-en-provence, Lyon, Toulouse) had no trouble chatting with me.
Also want to note that I am not passing judgement, I am sure I might become a bit brusque with tourists if Montreal had the same volume.
My wife was a French major in college and spent a year in Aix in the mid 80s. She didn't really enjoy the experience -- although her grammar and vocab were fine, she had enough of an accent that people treated her as an outsider.
On the way out of the country she stopped in Paris for a few days to take it in. She went into some shop and the proprietor asked my wife if she needed help. My wife replied asked about some clothes. The proprietor insulted my wife over her southern accent -- French southern, not US southern, and it made my wife's day. Someone in France finally thought she was french.
Also want to note that I am not passing judgement, I am sure I might become a bit brusque with tourists if Montreal had the same volume.