They are not. If anything they are a hell of a lot more polite than people are in New York or New Jersey (the other two places I've spent a significant amount of time living.)
Your odds of someone holding a door open for you, giving you a seat on a bus/train/metro if you are carrying a ton of shot or obviously sick/injured are much, much higher here than in America.
The odds of a people being friendly to you are also much, much higher. As far as I can tell, in New York, people go out and stay in their group. Here, people actually go out to meet other people and will be friendly outside their social circle.
If you are a woman, the odds of someone shouting shit at you when you walk down the street are much, much lower. And, if go out on your own, the odds of drunk dudes bothering you all night are much, much lower. People respect your personal space a lot more than they do in New York/New Jersey.
When out to dinner they also speak much more quietly - so, you know, you and your dinner date can also have a conversation without having to speak loudly yourself just to be heard.
Unlike in America, when you meet a new person the first question isn't "What do you do for a living?" People actually see you as a person and not a job and will ask questions about your life and shit you are interested in.
Plus, they'll actually ask you what America is like - and know shit about your country. As opposed to the majority of Americans I see come here who only know of The Eiffel Tower and La Joconde (and don't even know that it's called La Joconde.) (And don't get me started on the people who will go up to La Joconde look at it and leave the room without looking at any of the dozen or more as good or better paintings in that room.)
Yes, not everyone is perfect and, sure, some people may be curt with you from time to time. But, this usually happens when someone has been asked for the 474th time that day "Where is Amelie's dinner?" (the third place that Americans have all heard of) If someone in New York was asked over and over again in a foreign language where Ground Zero was they might give a curt answer as well.
This is not me saying France is perfect. Lord knows there are problems here. But there are problems in America too. And in the UK. And in Spain. And it pretty much every place in the world.
But at the end of the day, you know what's rude? Thinking a group of people are rude because of some stupid cliche that made it into American movies 40 years ago. That's fucking rude.