When I say that morality must have a personal (self-conscious) stopping point, I'm submitting that objective morality's ultimate definition is rooted in personhood. I would argue that both morality and rationality are inextricably linked to personhood. While your example of the dodo bird is well taken, the fact is that the dodo still existed at one time, even if all the specimens are extinct, so the concept of the dodo bird is inextricably linked to the prior existence of the dodo bird.
In the case of objective morality, it must be tied to the ultimate nature of existence (again, atheism, pantheism or theism). There must be some sort of ultimate paradigm of goodness that distinguishes it from evil, and an impersonal explanation simply doesn't cut it. Concepts like goodness, love and rationality are not merely related
to personhood—they are inseparable
from personhood, so I would argue that none of them could exist apart from personhood. In a cosmos devoid of personhood, there would be no rationality, love or goodness, as there would be no self-conscious (personal) mind of any kind capable of having such traits. There would only be mindless machinations (as many atheists have ironically admitted). However, I understand you disagree with me on that point.
Regarding why I said evil is parasitic upon goodness, I went into great deal about this in my post If God Is Good, What Is Evil?
The short version is that, like falsehood, evil only gains its definition by warping or attacking goodness. For example, rape (evil) is just a perversion of sex (good). Murder (evil) is merely an attack on life (good). It's similar to how facts (truth) stand true on their own, while lies (falsehood) are only distortions of or contradictions to truth. The existence of truth opens up the possibility of falsehood, but only if something contradicts truth. Truth does not need falsehood, but falsehood does need truth. Goodness does not need evil, but evil does need goodness. The important point is that good and evil must be separate
, and goodness must be entirely superior (necessary) to evil—yet only theism provides a valid basis for this. Under atheism or pantheism, everything is either part of the self-existent material cosmos or the self-existent spiritual cosmos, including good and evil—in which case good and evil are equally valid and necessary parts of a greater whole. But I firmly contend that the classic New Age assertion of "there is no good without evil" is 100% false. Again, I went into this issue more deeply in the other post, though I kept it separate from this thread, in order to attempt to keep things shorter.
In terms of what makes a good person, I delved more deeply into the question in my post The Moral Argument for the Christian God Alone
. Again, it may be best to discuss the issue under that post. Or you could peruse my other two posts and raise objections in this thread (whatever works best for you). I find your definition of a "good person" to be insufficient, as there would most certainly be an amount of goodness needed! If no amount is needed, then the argument about a "habitually good person" disintegrates, since a person who habitually does 0% good deeds would still qualify as "good", and no habits are needed in the first place. "Habitually" must be quantified or defined somehow, and that inevitably leads to an amount—some sort of dividing line between a "good" and a "bad" person, possibly with "mediocre" people in between. On the other hand, if there is a percentage requirement, the question immediately arises: is it 21.2%, 98.9%, or 52.645902%? What exactly is the magic number? How good is good enough? Were Stalin and Zedong "good" people? If not ... how did they fail to objectively qualify as "good"? Also, since the method of justification, namely qualifying as a "good person", stems from the self (i.e. the level of habitual goodness or the number of good deeds or the percentage of righteousness or however it's captured), the logic is still firmly rooted in human self-righteousness. And as I explained in my post, even evil people actually think they are good. This is the joke evil plays on itself. Falsehood is really just bogus truth, and evil is really just bogus goodness. And out of all the religious and irreligious teachers in human history, Jesus alone challenges human self-righteousness (a.k.a. evil), which is why we all attempt to avoid Him and conjure our own raised-in-rivalry-to-God goodness (per the narrative in Genesis 3).