Damn you went all out with the absurdity of that straw man. Nice one!
Politicians are constantly criticizing their opponents without necessarily presenting alternative solutions. A murder done with a political motive is a political murder. A political murder is a political message. “The system sucks so bad that there are people out there who are willing to take arms because of it.” That’s the message, in case you seriously still had not figured it out yourself.
The book was only referenced in order to emphasize that political motive by bringing up the fact that the health insurance sector is rotten and many have grievances against it. The methods the author would prefer are irrelevant to that fact, as the shooter clearly arrived at a different conclusion.
I’d say that yes it was definitely at least partially politically motivated, since it was just as much an attack against the system as it was against the person, but hardly terrorism since there was no intent to scare the general public.