Well to give context to the situations. It was after the First Armageddon War which was a big Chaos incursion. The Inquisition decided to take the survivors and sterilize them and let them die off in labor camps. The Space Wolves protested that, and the Inquisition decided this was grounds to start a war with a loyal and very powerful Space Marine chapter.

The other one was just referencing how the Inquisition can, depending on who is writing them, be utterly trigger happy with an Exterminatus. Sure there are times when it's a necessary evil but we also have cases them doing it over petty things like contact with aliens or alien technology.

The last bit was with the Imperial Guard with an officer named Kubrik Chenkov. The guy is a complete idiot whose solution to everything is throw wave after wave of men at it. Sees a mine field? Throws waves of men at it to clear it for his tanks, sees melee enemies, he throws men to bog them down so his artillery can hit them, and once executed men just so he could use their bodies to make a damn. And the Imperium considers him a hero.

All of these are ideas much worse than letting a teenager pilot a Titan. Hell the war started with the Space Wolves probably cost several Titans.

The last part was a joke. Because only the Imperium of Man would be so crazy as to call a planet Armageddon.