To say we don't need All-News at night is silly. If you want news at 3pm, you want it at 3am. If you need traffic and weather at 1pm, you need it at 1am. Again, to say there's no traffic overnight is silly as well. Plenty of overnight construction projects close highways. If a truck can overturn at noon, it can overturn at midnight.
Now, if you say that Boston should have more than one Talk station, I'd agree with you there. Maybe that's why some folks say WBZ should do Talk at night, because the only other option for nighttime talk is WRKO. If you're not a fan of Coast to Coast, you're out of luck. Even the NPR stations, WBUR and WGBH, don't really do regular programming overnight. They either run Public Radio Exchange or BBC World News. Sometimes both stations are running the same program. They should repeat some of their shows from earlier in the day for late night listeners who may have missed or been asleep for the daytime shows. WNYC NYC repeats its local Talk shows at midnight, one on the AM, one on the FM. (I'm surprised NPR hasn't started a late-night Talk show, since most NPR stations simply go with the BBC all night.)
As we've said before, all the other CBS All-News stations (except KRLD Dallas) do news overnight. If I turn on the hot water at my kitchen sink, I expect hot water to come out, all times of the day. I don't expect apple juice between 8pm and 5am, as nice as apple juice might be.