People have been talking about multiverses as a philosophical idea for a long time. But the current incarnations in physics, I think, are more indicative of problems with some things going on at the frontier of physics than ideas that are gonna last.
'Thou shalt not kill' does not apply to murder of one's own kind only, but to all living beings and this commandment was inscribed in the human breast long before it was proclaimed from Sinai.
The past is past, and the future is yet to come. That means the future is in your hands - the future entirely depends on the present. That realization gives you a great responsibility.