You had to put Cheney and Rumsfeld together. In the movie, Rumsfeld was Cheney's Cheney, the kind of bad influence on Cheney that Cheney was on Bush. Then the filmmakers could show less unattractive aspects of Cheney - the befuddled young man, for example, or the supportive father of his gay daughter - and still paint a very negative picture of him.
The film showed Cheney to be less ideological than many critics thought he was. Did that make him more sympathetic or less sympathetic? Maybe a mixture of both. In the film he wasn't trying to do evil, but not trying to do good either. He was in it for himself. But was he really trying to get power or just trying to survive in a highly competitive environment?
I wasn't a great fan of any of those guys, but the bias was obvious. You're right in thinking that it wasn't entirely negative. Certainly not positive either. I think the style of the movie - in your face and stupid - cut against any nuance in the script or performances, though. Same thing with The Big Short and everything else the director has done. "Subtle" doesn't really work with him.
It showed Cheney as somewhat ethical because he would not criticize his lesbian daughter. However, later in the movie, it torpedoed that when it showed he gave his other daughter (Liz) the go-ahead to oppose gay marriage when she was running for Congress.
In my last post, I should have said “sympathetic” instead of “ethical”.