Regarding killing the demons, yes, Krsna has done it. "paritranaya sadhunam/ vinasaya ca duskrtam [Bg. 4.8].'' But, for us to kill like that we first have to become first class Krsna devotees like Arjuna or Hanuman, then we can fight with the Ravanas and demons. But that requires good strength, and we are not in that position now. Caitanya Mahaprabhu did not kill the demons, but He converted them. So this should be our example.
Letter to Hamsaduta Das, 8 November, 1973