Yes.
For those who don’t know, the Associated Press (AP) is a news wire service. Many, many journalistic organizations use AP stories as a basis for their own news, or just directly use the stories from AP due to their reputation for extremely quick, accurate news.
AP Style, created by the Associated Press, is the generally-accepted style and set of rules for journalists. The AP Stylebook is put out every spring, and is often carried on a journalist’s person and actively referenced when writing articles.
(Source for these things: my soon-to-be 5 and a half years of studying journalism in college, in preparation for my career in the field.)
By AP stating that ‘alt-right’ should not be used and ‘neo-Nazi/white supremacist/racist’ in its place, it’s basically not only an open call, but a direct demand that journalists don’t use alt-right and instead use the other terms.