1 Sentience (ability to feel pleasure and pain) is what matters, not biological meaning of life.

Why is sentience important? Is it okay to piss on a person's grave just because they aren't sentient anymore? If someone drowns in front of you, is it suddenly okay to kick over a person's sand castle just becauee theu aren't sentient anymore? If you numb someone's arm so that they can no longer feel pleasure or pain in that arm, is it okay to cut it off with a hacksaw? If something bad happens to a forest, but the forest isn't sentient, isn't it still bad? Isn't morality supposed to be about reality? Do you actually respect the things that sentient beings care about? Or is morality just a meaningless checklist of creatures whose perspectives you can safely ignore just because you aren't causing them any physical pleasure or pain?