Police were clearing Castle St when the teen approached their patrol vehicle and said words to the effect of: "Muslims are not welcome in our country. Go home Muslims".
Brittenden argued he was exercising his freedom of speech and called police "right-wing fascists".
While the discussion progressed, three women told the officers the defendant had earlier been repeatedly shouting "f*** the Muslims".
He was then arrested.
Brittenden wrote a letter to the court stressing his shame.
"I want you to know that this moment of drunken anger and utter stupidity is not at all a reflection of my character, but rather a brief moment of chaos," he said.
"I'll admit I've done some stupid things on a Saturday night but this was on a whole new level."
After the hearing, Brittenden told the Otago Daily Times he was not a racist.
He had been drinking all weekend before the incident and did not know the horrific scale of what had happened in Christchurch at the time, he said.
Brittenden also told the ODT he had a Muslim friend, whom he had contacted after the shooting to ensure he was safe.
He absolutely rejected the notion he had any extreme political views.
"I want to make it very clear, I wasn't celebrating what happened in Christchurch. It was me being a drunk idiot, saying offensive stuff," Brittenden said.
However, a former flatmate - who spoke on condition of anonymity - said the defendant had made racist comments before the March incident and had once donned a Ku Klux Klan-style hood.
Brittenden said that had actually been a friend of his.
He suggested the ex-flatmate might have been trying to "stitch him up" with the allegation.
Another flatmate made similar claims of racist comments being made by the defendant in their shared accommodation.
Brittenden again denied it and said it could only be put down to "Kiwi banter" that might be explained by a language barrier between him and a student from overseas.
The defendant's father, Scott, said after hearing of his son's transgressions he immediately travelled from Christchurch to get his son help.
Together they enrolled him with a psychologist and Brittenden made a $500 donation to the victims of the mosque shootings.
Mr Brittenden said it had been the most disappointed he had ever been with his son but he had seen a great change in the teenager in the past three months.
"He was an idiot and stuffed up but you've got to learn from your mistakes and rectify the situation," he said.
Counselling might address Brittenden's drinking but Judge Macdonald was worried about the defendant's beliefs.
"You may have been intoxicated but where did these views come from?"
A University of Otago spokesman said now the court process had concluded, it would consider whether any action was necessary under the code of student conduct.
The penalty the court imposed would be taken into account, he said.
Mr Brittenden said yesterday they would see the proctor straight after the court hearing.
"He's going to man up and take responsibility," he said.
