He was a patriot. What would you have done in his place? Betray your own country?
Of course not. Patriotism is always honorable. As long as his orders are lawful, and his violence is directed strictly at combatants, there is no dishonor in the soldier’s bloody task — even if the country for which he fights is in the wrong. It is the instigators of war who bear the blood of war on their hands — not the soldiers.
Yes, it would have been nice if Herr Severloh and the rest of the German army had simply given up on 6 June 1944. It would also have been nice if Hitler had been accepted into art school in 1907 and skipped the whole “Third Reich” thing. That’s not the way things worked out in either case.
As things did work out, Herr Severloh did what any patriot would do in a war — he killed for his country. I would hope that you would do the same were you to find yourself in his shoes some day.
And if I was in his shoes, coming off the Eastern front I'd have probably swam the Channel at the first chance considering Hitler's leadership and what he had done to Germany. In June '44 Severloh knew Stalin had over 1,200 divisions crossing into Poland versus the few dozen (actual) German divisions. The only thing slowing the Red Army down was the supply lines.
The Normandy Wehrmacht divisions had many E front re-assignees like Severloh so it was well known there was no way in Hell the Red Army could be stopped. They were not patriots they were ideologues who were committed to fascism and so they fought on. Imo they should all have died with Hitler, particularly the 'patriotic' zealots. The POW camps in France did a good job of it after the war where over a million German POWs met their end in a similar fashion to what Germany did to millions of Russian POWs 4 years earlier.