The judge said the Korean man and his family were walking in George St, about 4pm, when Mercer and three associates directed racist verbal abuse at them and made comments about their ethnicity.
Told by a member of the Korean man's family to "back off", Mercer and his associates followed continuing the abuse.
A female associate of Mercer who was sentenced last week threw a wine bottle at one of the family members.
Soon after, Mercer advanced on the Korean man and punched him in the face.
About 5.40pm, in Filleul St, Mercer approached the second victim and asked him for cigarette papers. Saying he had none, the second victim turned to walk away. But Mercer pushed him forcefully in the back, and when asked what his deal was, spat on him resulting in a large amount of saliva striking the front of his T-shirt. After a short argument, Mercer grabbed him by the shoulders then punched him once in the face, knocking off his glasses, which smashed on the ground.
At the police station, Mercer became hostile and spat at a constable causing saliva and blood to strike the front of his vest.
The assault on the Korean man caused bruising and slight swelling near his left temple.
The second victim and the constable were uninjured.
Public defender Catherine Ure submitted it had been "an afternoon of spectacularly bad behaviour" by Mercer. Because of the alcohol he had consumed, he had little memory of what happened. Mercer recognised being drunk was no excuse for lack of self control and was "embarrassed and ashamed to be here". He accepted responsibility from the outset and pleaded guilty at an early opportunity.
Judge Coyle told Mercer it was entirely unacceptable and abhorrent that anyone should be taunted simply because of their race "or looking different from you". The racist nature of the taunts and "bully boy" tactics were aggravating factors.
Mercer was charged under the Crimes Act with assaulting the two members of the public and under the Summary Offences Act with assaulting the constable.
On the Crimes Act charges he was given two-month sentences of home detention, and on the Summary Offences Act charge one month (all terms concurrent and with special rehabilitative conditions). In addition, he is to pay $175 reparation for the assault on the second victim.
Standard post detention conditions are to run for six months past the detention end date.
