Sirius does have that effect, and most of the time, he doesn't care that he's doing it.

"Your brother the blood traitor?"

Regulus isn't the only one who had lost a brother after Sirius' first year at Hogwarts. Sirius had tried to get Regulus to listen to him, unsuccessfully, and still remembers how it had felt the first time his younger brother had used their family's favorite insult on him. It had stung, and maybe he had been wrong to consider Regulus a lost cause after that, but what else was he supposed to do at the age of twelve?