M*A*S*H was highly disrespectful of the military. Col. Potter was the first “regular military guy” who wasn’t written to be despised. In the TV show taken solely on its own merits, this is excusable because it’s written from the POV of characters who would do anything to leave the war. My father is a Korean-war veteran who sympathized with this perspective, even as an enlistee. But in the larger context of Walter Cronkite, Jane Fonda, John Kerry and the generally anti-American portrayal of the military in Hollywood, I could easily understand your father’s reaction.
Harry Morgan, played a crazy general in an earlier MASH episode before he became Colonel Potter.