If writers were smart to explore it, Peter would have accepted killing long ago to comphrend the same things a police man or a solider would when faced with a serious issue of upholding human lives in the long term and placing the integrity of life without constraints of moral simplicity. Peter should figured out that people still die or suffer even when one doesn't kill a enemy for the longer-term.
Even Deadpool in one his issues understands that its better to kill evil than to save it or prevent it from being able to kill another day in cold blood. Spiderman is hardly in any position to preech what it means to be responsible as person who has destroyed as much live as hes saved in his life as a heroic figure of community service.