OK seen it, now barring the late hour and street full of drunks what did they do that they shouldn’t have? If you answered pursued and confronted the drunk give yourself a kewpie doll for mental clarity. The minute they pursued and confronted their assailant they became the aggressors. Now their actions didn’t appear to warrant the drunks response but if things had escalated you can be assured that lawyers types would not look too kindly on the assailant being chased down.
So what should they have done? Exactly what Tam suggested if they really felt it warranted a confrontation. Call the uniforms and let them deal with it. Sometimes being in the right means swallowing a bit of your pride or dignity to either avoid or deescalate a confrontation. That is part of our responsibility as an armed citizen.