The thing your forgetting is that Thanos had to grow into being the deeper more philosophical character. In the beginning he was very much a world destroying mad titan with no real depth to this character. Even Starlin has used this fact in his stories when he has Thanos refer to his past.This comic in particular was controversial because of how it flew in the face of Thanos's established lore for the sake of making him a more simplified and by the numbers villain, to say nothing of Aaron's inability to write cosmic characters different than characters from a street level thriller. Marvel Cosmic has always been fairly self-contained and internally consistent because after Kirby, only a handful of writers actually tackle it in the first place, and it ended up dividing a lot of people in the process. Was Starlin's take on Thanos a sacred cow that shouldn't be contradicted because he was the character's creator and his stories are classics, or is it okay to throw implications about Thanos's origin by the wayside in favor of an unreliable narrator approach that contradicts earlier authorial intent? That was what most of the discussion about this comic boiled down to. I'm firmly in the pro-Starlin camp of course.
We know Thanos was a kill crazy little SOB "back in the day". Why are you upset with a past that actually shows it?