"it's a bad moral choice, there aren't enough rewards for nuking megaton! you can get all those caps easy in the lategame! if you try to turn burke into the sheriff instead, burke kills him and he drops one of the best assault rifles in the game early!"
The optimist in me wants to give them the benefit of the doubt. People do good and evil playthroughs all the time, but if a decision will harm you "materially", then they would likely not do it even if it conforms with one doing an evil playthrough.
For example, on a few good playthroughs of Skyrim I became a vampire so I would never have to worry about diseases and the vampire lord form saved my ass multiple times. For role play purposes, I just fed on random bandits who I was fighting anyway.