I disagree. Lightside BH makes perfect sense, especially when Tormen threatens harm to your companions (force chokes Mako) and the BH has a realization that what Tormen is making him his pet.
Remember "The only law in the galaxy is the one a man makes for himself" -that's the lightside ending. You are a hunter with ethics, you are to be honorable even when it means going against contract.
It's not I like him, but Jun Seros and the chancellor are far worse to you. They framed those crimes to you and launched those cruel operations. You had your chance to avenge yourself because of Darth Tormen's help.
Remember those BH who got killed by the Jedi? And your companion got kidnapped because of those framed crimes.