* In real life, to my knowledge, all US fighter pilots are required to have college degrees. Assuming this holds true for the Galactica world then it makes sense that, when faced with a lack of trained lawyers in a ~40,000 person population of mostly military personnel, he may be one of the most educated people available to fill the role. Also, most people couldn't have been trusted to give Baltar an honest defense or, more likely, would never have been willing to be his lawyer in the first place.
This and the episode with the fuel production crew going on strike pretty much killed any positive opinion I had of the show. Let's examine the situation: 40k people, mostly civilian. A handful of highly trained military including fighter pilots, a necessary component of warfare as conducted in the series. Training new pilots is an expensive and time consuming proposition, you have to spend a substantial amount of time at each location to train, I'm not saying days, but at least a day to plan and then execute training sorties. You have to have the resources to fuel them, which given how they spent a whole episode hunting down a source for fuel seems to make it rather rare. Now, take the second best pilot (as I recall he's the best technical pilot, and Starbuck is the best pilot) in the fleet, and tell him, "Yeah, it's ok to quit now, we don't really need you." Then you have to waste weeks to train someone else to fill his slot, of course they won't even be close to his skill level so it won't really be a replacement. The only thing keeping the remaining human population (at this time in the series) from extinction was the military and the fuel. Why would you throw it all away because you have daddy issues?