Why is it important to honor all life as sacred?

 Because in honoring all life as sacred you also honor your own life and then preserve your own life and all those lives around you too.

So, taking care of life around you allows you to continue existing and living too.

Because if you do NOT honor your life and all lives around you what's to stop you from killing yourself and everyone and everything else in your life?

What's to stop you from nuking the whole world out of existence with everyone on it in a blind rage of anger?