TU, to answer your points -

"1. The police is just conveying what the suspect said."

Why? What's the point? It serves no purpose to publicise this.

"2. We can't be absolutely sure it wasn't foreign but Japanese a drug dealer. There are actually many Iranian or Nigerian drug dealers in Tokyo."

Firstly, do you really think the majority of drug dealers in Japan are NOT Japanese? I'm not talking 'street' dealers here. And do you really think that someone who's confessed to buying drugs for a long time (a celebrity) goes out to buy from an unknown street dealer each time? That's absurdly risky.

"3. Noriko's husband might have purchased drugs from Japanese mafia. If that were the case, blaming a nameless foreign drug dealer would be safer than ratting Japanese mobsters."
He might have done. (Let's be honest - he probably did.) So yes, I can understand he doesn't want to say that. But that's got be clear to the police, so why do they report "it was a foreigner"?

"4. That kind of utterance is an universal phenomenon. (I heard the similar utterance in Europe.) People are the same everywhere. I don't think your argument is necessary."
Really? I haven't. In fact I just had a quick look through a British news source, and NOT ONE of the stories mentions the dealer.

I've heard it's much more common to say you don't know the guy the bought them from, it was just a guy you met once, you don't know who it was. No need to invent a story that cast shadows of doubt on thousands of people. But even if you do, there's no need for the police and media to jump on it.

It seems like you are almost confessing with it that you have the xenophobia vice versa you referred to. I guess if you changed your attitude you would find it differently. Unless you can change those people, just take it easy.

TU, just to be clear, when a police suspect names "foreigners", I only find that annoying because the police and the media take such delight in reporting it. When it's reported on every news programme, it appears like an important factor, whereas really it's clearly a cover story in the vast majority of cases, so it's an irrelevant detail. If they didn't report it,　the damage wouldn't be done.

Please don't accuse me of xenophobia when all I am doing is pointing out that the police and media are impugning the reputation of all non-Japanese residents with this needlessly careless reporting.

Japanese attitudes towards gaijin are quite well known, Tofu Union. And just because you heard something similar in Europe does not make what happens in Japan any less comment worthy.

By the way, do you know what "xenophobia" means?