I'm not saying you're wrong because it's your opinion as you stated it but I think things are a little more diverse that what you saw or witnessed.
First, you're right about the following :
- Sons of immigrants (mostly from African descent, whether Northern or sub-Saharan) have difficulty to "assimilate" as French because of the country having difficulties to accept them but also because they tend to strongly represent their homeland ("le bled"). It's a common reaction that sons of immigrants (born here) do. But it's not only from Africans, people from Portuguese, Italian, Spanish, Belgian, West Indian, or other east european descent do it also. If you look at cars, you will often see stickers from their homeland : the Portuguese Order of Christ symbol, some flags or some words in Créole or other european countries.
But it's also because France has many regionalisms : by that I mean, there are region swith strong identity in which a good amount of their inhabitants will identify as is more than as French. Corsicans, Britons, Northeners, Alsacians, Basques, Catalans are some of the ones who also identify by their region more than the country. What the sons of immigrant do is nothing more than what regionalists do, the different being that what their identify with is a foreign country or a french island.
- The Anthem has been boo'd at international events by french from northern african descent. In Football matches, it happened in a France-Morocco a decade back, in a France-Tunisia a few years back. But it was also boo'd by Serbians a few years back and by Belgian people last year. It's not unusual for the anthem to be boo'd unfortunately.
France has troubled relations with Maghrebis (and Africa in general) because of the Colonization and how it was reluctant to give freedom to those people and the country now pays the price because the sons and daughters of those people are still mad at it, considering how badly the country treated their parents. Parents that never really had problems themselves and was kinda satisfied of their situation but the sons felt like they were not welcomed and it was bound to happen since the lyonese Marche des Beurs (The Arabs March) in the early 90s demanding for more equality. I don't know about the UK and how you dealt with the Colonization how you still have the commonwealth but it looks it was done peacefully. Unless we're talking about Argentina
What struck me in you post is that you were talking about "colonies" as if those other commonwealth countries are still dependencies. Maybe that's the difference between you and us, as France decolonized (violently for a good part) those countries and that cause the bound to be torn if not broken for some and maybe that's why the relation seems bizarre for you.
But speaking of football matches, I remember in 2006 during the World cup, I was at a stadium with a few thousands of people during France-Brazil when we beat em 1-0 and even if those brehs had African countries flag with them, they all erupted in joy when Henry scored. I was at France-Portugal for the semi and the french brehs from Portuguese descent were rotting for Portugal and were mad that they lost while the brehs from African descent were for France and were happy they won. Same with the French from Italian descent supporting Italy during the final and shytting on us when we lost.
I feel like they feel french to some extent but not totally above all when their (supposed) homeland is in the mix. They will always support their homeland if France meets it but will support France otherwise above all when it meets a rival country of their homeland. It's a troubled relation from both sides really.
But, where I think, you're mistaken is about Black people being the bottom of the ladder : yes there are rough areas where crime and unemployment is high and yes people there are mostly immigrants or from a foreign (african mostly) ancestry but that definitely doesn't mean that all people from African descent are in poor situations. You take Paris as an example but at the same time Paris is and is not France. It is as it's the capital which gathers everything and problems are way more but it is not as other parts of the country are really different. I don't know which part of Paris you visited but the Northern and Eastern districts are the least favoured and it is, historically, like that. So if you resided there, your view on the issue is understandable.
If you want to see black people in suits, go to the Parisian business district in La Défense (the equivalent of the Londoner City), you'll see plenty. It's about where you look. Obviously, in poor areas, it will less be the case.
Here's pic of people eating at lunch time on the steps of the Arch (I worked there in a summer jobs a few years back, and I had a suit... most of the time
)
It's mostly white (France is) but you don't need a minute to find a Black, an Asian, or an Arab, they are here. It may not be as diverse as in the City business district but it still is.
The french motto is "liberté, égalité, fraternité" (liberty, equality, fraternity) but it's a motto, that doesn't mean it's effectively the case... Do all Americans put their trust in God ? France is still a mostly white country and integrating people from different culture, with different language, with a different ethnicity takes times, generations. People from Polish, Spanish or Italian immigration were hated in the late 1800s / early 1900s because they were different (and they were white !) and were taking jobs from the very french. Now those polish, spanish are french and you couldn't tell their ancestry if they hadn't a foreign sounding names.
So you gotta let the next immigration wave takes place and settle because we are progressing : the Justice ministress (one of the five biggest ministries) is black, the Overseas ministries is black, the European Affairs state secretary is also black. In the government, there are 6 out of 30 heads who are non-white. That's 20%, and I can assure you out of 65M, there are no 13.5M non-white french : in 2004, France was to be 87% white.