Frank's hypocrisy

This is what Frank said in the very beginning, and is a good description of how he turns out himself:

"It doesn't matter how politely I ask them to practice some common courtesy. They're incapable of comprehending that their actions affect other people. They have a complete lack of consideration for anyone else and an overly developed sense of entitlement. They have no decency, no concern, no shame. They do not care that I suffer from debilitating migraines and insomnia. (...) I know it's not normal to want to kill. But I also know that I am no longer normal."

So, Frank knows he's not normal. He must be sick because society and people around him has made him sick, according to himself. However, he develops an overle sense of entitlement himself. Entitlement to decide who should live and who should die. He is also incapable of comprehending how his actions affect other people when he goes on his killing-spree. He doesn't care how it affects the families left behind etc. No decency, no concern, only shame. Shame over himself and the society he lives in.
Does this make him a better person? I think not.

Also: solving problems with violece and death is just another sick, twisted thing to do, only making society even more sick. Frank is frankly pissing his pants to keep himself warm. It backfires.