‘Boston Public Radio,’ with Jim Braude and Margery Eagan (WGBH weekdays from 11 to 2) features interesting guests and discussion. Except for the call-in segments. That’s when Margery and Jim pick a topic, riff personal rants, and throw open the lines for others to complain. I don’t see the point, except perhaps to illustrate that talk radio dialed left can be every bit as angry as talk radio dialed right. And on ‘Boston Public Radio,’ the favorite rant is: traffic. Lines light up, vitriol spills, and nothing changes.