It has been said that the French revolution was enough to make anyone cranky, especially with the onslaught of such political and social upheaval. So following years of violent turmoil and executions as a form of repression its understandable why the French have been a tad bitter in the past. Their Animosity towards foreigners have been one of "well why did we have to go through that and nobody else?" It has been argued, but not at any conciderable length - that this opinion is without base or reason.
It is also a point of contention that the French language is of the highest form because diplomats and policy makers world wide are required to at least learn it. So when foriegners speak to native French citizens without so much as a local "hello", there is little hope of expecting a pleasant reponse...
...or at least a response that does not involve spitting.
I have to say honestly, that they are no worse than anywhere else. Not at any point was anyone in Paris rude to me. Personally I think you have to be unbelievable rude to get a rude response in return. And if you dont want to be barked at by an angry french person then stick around western areas.