I found the "war-crazed admiral" storyline by itself silly and cliche.
Yes, but well done, imo.
At least Marcus wasn't going around saying Klingons were trying to pollute our precious bodily fluids.
I didn't have a problem with Marcus, either, even though he was over the top, son. In reality, Marcus struck me as grossly exaggerated and totally amoral versions of Curtis LeMay and Douglas MacArthur who somehow avoided any checks on his power or ambitions.
After all:
-- LeMay told anyone who would listen (even in public) that nuclear war with the Soviet Union was inevitable and major U.S. cities would be wiped out. In 1961 he told JFK he had a plan for a surprise attack on the USSR to beat them while the U.S. still held the nuclear advantage. Kennedy didn't even listen to the plan.
-- In October 1962, when Kennedy said no to LeMay's plan to bomb the missile sites in Cuba and went with a blockade instead, Ted Sorenson said LeMay likened that to Chamberlain at Munich and said the American people would never go for it.
--Think of how badly MacArthur wanted to escalate the Korean War to use it as an excuse to invade China.
So, is it that much of a stretch to create a grossly audacious character with an itch for war with the Klingons that has to be scratched?