@researcher111
The U-boat commanders could hardly been held responsible for how the prisoners were treated after putting them ashore. I can easily list you over a hundred events where they helped Allied survivors after sinking their ships respectively when they encountered lifeboats or rafts. How many cases can you list where survivors were mistreated or refused help by U-boat crews?
Schlippenbach literally wrote in the war diary of U-453 that he was sorry: "Hinterher tut es mir leid, dass ich den Männern nicht Brot und etwas Wasser zurückgelassen habe." (Afterwards I'm sorry that I have not given bread and some water to the men.)
Incident #2 listed in this thread is one example where the decision to rescue Allied survivors was made for humanitarian and not military reasons. U-206 was en route to its patrol area and it would have been reasonable not to take six enemy men aboard for the duration of the patrol, but Opitz wrote in the war diary of the U-boat: "Ich hätte sie mit frischem Proviant versehen und weitertreiben lassen können. Andererseits hätten sie mit eigener Kraft niemals die 240 Seemeilen entfernte Küste erreicht, sie wären umgekommen. Das erstere wollte ich nicht, das andere konnte ich nicht übers Herz bringen." (I could just have given them fresh provisions and let them drift. On the other hand they would never have reached the 240 nautical miles distant coast by their own power, they would have perished. The former I didn't want, the other I hadn't the heart to do so.)
In this context the article
Treatment of Merchant Ship Survivors by U-boat Crews 1939 - 1945 might be of interest and perhaps the book "Neither Sharks nor Wolfes" written by Timothy Mulligan.