I don't want to state the obvious and repeat the points made by others as how bad booing is, etc.-this was already covered by previous posters numerous times.
What I wanted to cover is Sala's (Milano mayor) proposal to give captain's armband to Asamoah for next match. The interracial and multicultural relationship topic is extremely delicate, as is the subject of immigrants and refugees. I've never lived in Europe so can't experience the day-to-day issues of cohabitation of different people with different culture,language, historical background, etc.etc.hence I can't judge anyone. Personally I've been raised in multicultural bilingual community and haven't ever experienced any racial tensions in my country, actually the first time I've ever seen people treated differently because of their race or skin colour was in US.
So, the proposal to give Asamoah's armband because of how Koulibaly was treated really stinks, for me it shows that Sala is a covert racist himself. What's the point of doing that? "Black Economic Empowerment","Affirmative action, like in post-apartheid South Africa? We want to promote a society where everyone is treated equally regardless of their age, sex, race,etc. and yet after a player with black skin was booed we want to give captain's armband to another black player? Thus effectively proving that skin colour matters and is a way of how people distinguish from each other?
I also can understand why BEE was established in South Africa and that's a benevolent deed in a nutshell, cause it was established to help redress all the inequalities of previous political regime. I don't want to cover cases when social background actually became the most important factor instead of qualification and experience now.(hence cases when people with white skin were disavantaged when considered by a potential employer). The thing is, the idea was to mitigate all the inequalities of the past.
But Asamoah's case is different. He became a player of a top clubs like Juve and Inter purely because of his skills, his tenacity. He wasn't negatively discriminated because he was black and so worse midfielders played instead of him, nor he was positively discriminated, as if he had shit skills but was bought by Juve because they had to have specified number of African descendants in their squad. He made successfull career because he is a good player, simple as that,regardless of skin, white,yellow, black, or gray-brown-crimson. And now covert racist Sala wants to give armband to him because he is African and black hence we need to please him. No, we need to have a society of equal opportunities and treatment. Giving armband to person because he is black is not acceptable way to treat this problem. In my opinion this is a huge insult of Asamoah.
Sala probably proposed that with emotions and he isn't a racist himself but his subsonciousness is clearly racist, he just can't acknowledge that.
Re what forzainter said, I was always amused how foreigners most of the time treat a person with epicanthic fold as a Chinese. In Turkey people think I am Chinese, even in Russia some people think so too, whereas I can (9 out of 10 cases) distinguish Kazakh, Uzbek or other Central Asian person from Chinese one. In Italy I was greeted with "Ni hao" almost everywhere,same in Spain or France.