In France, saying "I love you" (Je t'aime) is not considered rude at all. In fact, expressing love and affection is a common and normal part of French culture. French people are often quite open and expressive with their emotions, including love and friendship.
The phrase "Je t'aime" is used between romantic partners, close friends, and family members as an expression of affection. It is considered a heartfelt and meaningful sentiment.
However, as with any cultural context, the appropriateness of expressing love may vary depending on the relationship and the situation. For instance, it might be more appropriate to reserve such declarations for close relationships or private moments rather than casual acquaintances or professional settings.
But in general, saying "I love you" in France is not considered rude but is an essential part of their emotional expression and communication.