I know this doesn't justify it at all, but I felt bad for House. I guess that was just his way of dealing with it.
I know this is a long shot and I may be reading far too much into it, but I think he may have been projecting his own anger at himself onto them. They didn't notice and they were his parents, and HE didn't notice even though he saw Kutner every day at work, probably saw Kutner MORE than Kutner's parents saw their own son. Despite this interpretation, I still disliked House immensely for it. In their time of mourning, the Kutners didn't deserve to be slapped across the face with House's own self-loathing.
I really feel that House just wanted someone to blame for Kutner's death. House likes things that are logical, and to him (and everyone else) Kutner's death was illogical. He wanted to find some rational reason for Kutner to commit suicide. I don't think he cared if he hurt Kutner's parents. It was more important to him that he make sense of a senseless death.
I think that's where the title of the episode comes from--"Simple Explanation." House wanted a clean, neat, logical reason for Kutner to commit suicide. He ran through everything that made sense. When those reasons ran out, he made it into a murder. What House can't handle is the fact that there may be no one reason for Kutner's suicide. There may be no one issue that broke him. It may be that Kutner was simply unhappy--and a lot of things may have contributed to that, including House.
In that respect I think you are spot on,
Ginna. House played a role (and arguably a big one) in Kutner's life. He was almost a paternal figure to him. Now he has to accept the fact that all his flaws and self-centeredness may have contributed to the unhappiness that led to Kutner's suicide. I think that House would rather find some reason, or blame some person, for Kutner's death than accept the fact that he may have driven, or helped drive, someone to suicide.