Journalistic freedom in the US has allowed American journalists and news organisations to publish a lot of untruths. The hurdle to prosecute for slander and libel is much much higher in the US than many other European countries. We can debate its pros and cons but that's the way it is currently and Michael Bloomberg would not be affected in the slightest even if it turns out the story is all toss.
This is especially so in the current "China threat" political climate in the US. China is essentially a boogieman in the US right now and attacking it has proven to be a great generator of votes for politicians.