Taking Hosts and Morality, etc. -β
Obviously, SpiderDudes are an alien species and so morality is different and not exactly comparable to human morality.
But! I think if pressed to try and explain it in human terms, Arakell would label what they do as 'mercy killings'. Their hosts are at death's door when they are taken as hosts. This is part of the whole shtick of taking a host in the SpiderDude's culture. The closer to death, the more 'difficult' to mend, the more impressive a host and thus the more impressive a SpiderDude you are.
If a host is taken that might have recovered without intervention, that is seen as a failing and that SpiderDude is seen as a weaker member of the society. It is tacky to take a host that might not have died, it is absolutely taboo and asking for ostracization to take a perfectly healthy host.
Arakell's host, Kevin Mathers, was going to die if not for his intervention, this is a fact. And one could argue the morality of saving a physical form just to let the spirit die, but just because you help a rabbit out of a trap, doesn't mean it's your responsibility to make sure the fox doesn't eat it. Etc, etc.
Arakell has no guilt over the all but physical death of his host. As far as he's concerned, it's just the balance of life. He is no different than a scavenger come to poke at a corpse and he feels no shame over serving his own species' functions.