I speak French reasonably well, but I was often treated rudely, particularly by people in customer service roles (my wife and I studied abroad). Clerks seemed agitated to have to deal with foreigners, taxis would blow off appointments, and even simple questions (e.g., asking for directions to a nearby building/office/etc) was met with "c'est impossible". In one case, my wife and I booked a hotel online, but upon checking in the clerk told us we had to pay for two rooms because my wife and I couldn't share a room. When I asked for an explanation, he said, "It's like putting 3 people on a 2-person motorcycle, it's just impossible!" (clearly he'd not been to India).

My French friends speculated that it could have been xenophobia or specifically that I was mistaken for an Englishman (I'm American, but apparently the French particularly dislike the English?).

At any rate, I had many positive experiences, and even these "negative experiences" weren't particularly negative (this was before being easily offended was fashionable among university students in the U.S.); it was more a neutral, cultural observation.