He was sentenced at the Old Bailey on Thursday to one year and seven months’ detention and one year’s extended licence.
He was also made the subject of a Criminal Behaviour Order for three years.
Mr Justice Jeremy Baker said Haynes “essentially became self-radicalised” and held “entrenched” racist, antisemitic and homophobic views.
“I am satisfied that not only did you hold entrenched racist, antisemitic and homophobic views at the time of the commission of these offences, but that these are views which you have not genuinely disavowed,” the judge said.
“It is apparent that you were not someone who limited your behaviour to the expression of your views online, but were prepared to put some of those views into action.
“It is of particular concern that not only had you asserted that one of your goals in life was to kill someone….but you had already carried out research as to the availability of one of the components for constructing a gun.”
A court order granting him anonymity under Section 45 of the Youth Justice and Criminal Evidence Act 1999 was lifted post-sentencing following an application from the press.
The anonymity order would have expired on Sunday when Haynes turns 18.
The teenager faced eight charges – two of possessing a terrorist document, three of distributing a terrorist document and three charges of criminal damage.
At a previous hearing, the court heard how Haynes was referred to the Prevent de-radicalisation programme last spring by the Royal Air Force Air Cadets.
Last September, he was expelled from the group after he sent images to other cadets bare chested with a Swastika painted on his chest and was banned from Instagram for posting racist and Nazi images.
The youth, then aged 16, went on to paint graffiti on a Windrush mural in Port Talbot, which celebrates the town’s Caribbean community, on two occasions in October and November.
Community members were shaken and disgusted after several swastikas, the phrase “Nazi zone”, white supremacist symbol “1488” and a racial slur appeared on the mural hours after it was completed.
The mural depicts Donna Campbell, a much-loved nurse and daughter of the Windrush generation who died during the pandemic, and her mother Lydia, known as Mrs Campbell in her community, with a merged image of a Welsh dragon and the Jamaican flag.
In October last year, Haynes was involved in setting off a smoke bomb at The Queer Emporium in Cardiff, which damaged the floor.
The emporium was targeted because it is a centre for the local LGBT+ community, the court was told.
Police searched Haynes’ bedroom after he was arrested on November 8 last year and found a stash of knives, an air rifle and antisemitic literature – including a copy of Adolf Hitler’s Mein Kampf which contained the defendant’s handwritten notes.
Other items from his room included gas masks and flags bearing a Ku Klux Klan (KKK) symbol and a swastika.
His electronic devices were seized and the court was shown homemade videos and images in which he made Nazi salutes and shared his far-right ideology.
His internet search history revealed a fascination with far-right mass killers and extreme groups such as the Atomwaffen Division.
The defendant’s diary also outlined a desire for “race war”, the court was told.
A list of life goals included “burn a building down, maybe bomb it”, “kill someone”, “join a Nazi militia”, “get a gun or make one” and “get buff as hell”.
One of the terrorist documents Haynes shared with another teenager gave details on bombmaking, derailing trains, attacking power lines and kidnapping police officers, as well as glorifying notorious mass murderers.
He possessed and disseminated another manual with “step-by-step” instructions on gun-making.
Haynes, of Cwmavon in Neath Port Talbot county, was sentenced to detention for terrorist offenders of particular concern.
He was given one year and seven months’ detention with one year’s extended licence for possessing terrorist documents, one year’s detention and one year on licence for disseminating terrorist publications and one year’s detention for aggravated criminal damage, all running concurrently.