Parisians are a whole different breed of people. Actually, that's too nice. They're assholes. I watched my Quebecois travelling companion speak in perfect French to a counter person, who virtually sneered at him before ignoring him completely and speaking to me in English. They've got being rude down to an art form, truly. Outside the city though, we got treated like long lost cousins - all due to his French. Same experience in Italy with an Italian speaking travel partner. Paris is, um, special, no doubt.
My wife speaks pretty decent French, which leads to amusing scenarios in Paris where she speaks in French to a person who insists in replying in (sometimes poor) English. Often they both persevere in the opposite languages to their own, leading to a weird inversion of what you would imagine would be the most efficient communications strategy!
I would guess there might be a few motivations for people to do this though, not necessarily just rudeness. Misplaced helpfulness, wanting to save face by not switching languages back, practicing English, who knows?
(What's really funny is when they finally give up and revert to French and then address a question to me - only for me to shrug with embarrassment and tell them I don't speak French.)
I wouldn't advocate being an asshole usually, but for Parisians speaking in English at you to be snobs, just compliment them on their impeccable English skills and suggest that means they must have some Englishman blood in them.
It may have also been what your friend said — French people are quite formal compared to Canadians and Americans — I know some French and was corrected a couple of times based on how I started the conversation: “Good evening” first, then start... most Americans at least don’t talk that way
Another 'politeness' example that can often trip people up is 'tu' offending people in France in situations where it would be perfectly normal in Quebec.
Everybody says this about Parisians, but I haven't found it to be true. I've visited Paris 3 times for a total of almost 3 weeks and met very few rude people. I've met a lot more assholes in Manhattan than in Paris. Of course, I follow the French rules of politeness. I always start with "Bonjour/Bonsoir" and always finish any visit with "Merci, bon journée/soirée, Au revoir." On the other hand, I've seen plenty of rude behavior by American tourists who just start speaking English to French people without any greeting or any attempt at French.
Canadian French is very different from France's, be it the accent, the idioms, the vocabulary.
As a native French speaker travelling in Montreal, I often found it easier to talk English with French speaking people, to my great shame.
I recall a simple transaction with a cashier in a supermarket, and having her repeat the simplest things (like "hello") a couple time because I had no idea what she was saying or if she even was speaking French, this was awfully embarrassing.
Parisians are SO awful. I studied abroad there for a year and was shocked to find that many of them (especially women my age -- and I'm a woman) were nastier than New Yorkers. All the French friends I made were a) not native Parisians and b) mostly male. But I spent Spring Break in the South of France and most people there were supremely kind and tolerated my accented French.
Weird. My partner and I visit Paris annually for weeks at a time. I've had maybe one or two rude experiences that I can think of. Everyone else I've encountered has been pleasant.
I am a very fat American tourist who has spent a total of two months in Paris in my life. I never met any impatience with my terrible terrible French from any Parisians at all.
I've been visiting Paris for 40+ years and I've noticed a distinct difference in sentiment over the past 5-10. Perhaps it's the younger generation or the freedom of movement within the EU or some other factors.
Good to know - I visited Paris at the end of the eighties, with friends, and it was a terrible experience. After two days we fled the city. I was yelled at when trying to buy metro tickets, because my pronunciation and word selection was slightly off - I remember I literally backed away several steps from the counter. Restaurants.. all bad. We met a total of two nice people, one young guy with a button which said he would speak English, and an old woman who didn't speak a word of English but still came running when she saw us studying a map. They were both very helpful. Everybody else? Not very much. Not at all, really. Train stations, other public services - speak perfect French, or get ignored (at best).
And at that time I had been travelling to lots of countries for years, and I never had any trouble communicating with people. Big cities, villages at mountain tops, desolated island towns. People were nice everywhere. Except for Paris.
If that has changed for the better recently then that's truly good news.