Perhaps they just like French culture. I don't think it really matters, though. They're in America, they can do as they wish.
Are my Finnish immigrant neighbors who learned French over English in California anglophobes or francophiles? Why or why not?
Don't make the mistake of trying to classify people you don't really understand. It's a major step down the road to bigotry.
Hopefully you won't commit violence against your neighbors.
Please leave your neighbors alone.