Many people that come in contact with the Primal Vow of Amida Buddha experience two types of reactions: they are happy in finding the message that is full of hope in the first part, but they get unsure right after reading the last sentence: "excluded are those who commit the five grave offenses and slander the right Dharma”.
“If it were only by observing precepts and upholding rules that we could entrust ourselves to the Primal Vow, how could we ever gain freedom from birth and death?”
In chapter sixteen of the same writing, while correcting the erroneous view that nembutsu followers must go through a change of heart every time they get angry or do something bad, Shinran said:
“Suppose that attainment of birth were possible only by going through changes of heart day and night with every incident that occurred. In that case- human life being such that it ends even before breath exhaled can be drawn in again- if we were to die without going through a change of heart and without abiding in a state of gentleness and forbearance, would not Amida's Vow that grasps and never abandons us be rendered meaningless?”
Because Buddha has Endless Compassion and sees every being as his own child, would be absurd to abandon them because of their ignorance. This attitude would be against the Bodhi Mind and the most elementary Mahayana vows. Buddha can't make a statement and immediately after, deny it or state its contrary, something like: "I will save you all even if you just say my Name ten times ...but actually, I changed my mind and I impose some hard conditions that you won't be able to cross".
Amida Buddha knows the true capacities of human beings and he didn't created his Vows for those capable of reaching Enlightenment through themselves:
“To destroy your blind passions means to become a Buddha and for the one who is already a Buddha, the Vow coming from the profound contemplation for five kalpas has no meaning.”
In Shinran's opinion, this "exclusion" actually shows that even the worst beings are included in the salvation of Amida, especially those who committed the five grave offenses and slandered the right Dharma. I think that the mentioning of these gravest offenses is a clue that they are not wanted in the disciples behavior but, in the same time, the effects of those offenses are annihilated by the Endless Compassion that is received in the believers heart through the awakening of faith. Probably, each of us, in our past lives or this life, we committed at least once one of these offenses, driven by our illusions or blind passions.
“Question: The Sutra of Immeasurable Life states,
‘Those who aspire for birth are all brought to attainment. Excluded are those who commit the five grave offenses and those who slander the right Dharma.’
The Sutra of Contemplation on the Buddha of Immeasurable Life states,
‘Those who have committed the five grave offenses and the ten transgressions, and who are possessed of various evils also attain birth.’
How are these two sutra passages to be reconciled?
Answer: The first sutra speaks of committing two kinds of serious evil act: the five grave offenses and the slander of the right dharma. Because of committing both these two kinds of evil act, a person is unable to attain birth. The other sutra speaks only of committing the evil of the ten transgressions and five grave offenses; nothing is said of slandering the right Dharma. Because a person has not slandered the right Dharma, he attains birth.
Question: Suppose a person has committed the five grave offenses but has not slandered the right Dharma. In the sutra, it is granted that such a person can attain birth. Further, suppose there is a person who has only slandered the right Dharma but is free of the five grave offenses and other evil acts; if he aspires for birth, will he attain it or not?
Answer: Although he has only slandered the right Dharma and has not committed other evil acts, he will definitely be unable to attain birth. How is this known? A sutra states that the person who has committed the five grave offenses falls into great Avici hell and fully undergoes their recompense for one kalpa. The person who slanders the right Dharma falls into great Avici hell, and when that kalpa has run out, he passes on into the great Avici hell of another quarter. In this way he passes through a hundred thousand great Avici hells one after another. The Buddha does not indicate any time when it is possible for him to emerge. This is because slandering the right Dharma is an evil act of extreme gravity.
Further, the right Dharma is the Buddha-dharma. Such a foolish person has already slandered it; how can it be reasonable to think that he would aspire to be born in the Buddha-land? Suppose the person aspires for birth merely because he craves to be born into happiness; this is like seeking ice that is not water or fire without smoke. How can it be deemed reasonable that he attain it?
Question: What are the characteristics of slandering the right Dharma?
Answer: Saying there is no Buddha, no Buddha-dharma, no bodhisattva, no bodhisattva-Dharma. Deciding on such views, whether through understanding thus in one's own mind or receiving the ideas from others, is called slandering the right Dharma.
Question: Taking such views only concerns the person himself. What pain and suffering does his act inflict on other sentient beings, that it should exceed the evil of the five grave offenses in seriousness?
Answer: If there were no Buddhas and bodhisattvas to expound the mundane and supra mundane good paths and to teach and guide sentient beings, how could we know of the existence of benevolence, righteousness, propriety, wisdom, and sincerity? Such mundane good would all be cut off, and the sages of the supra mundane would all perish. You know only the gravity of the five grave offenses, and not that they arise from the absence of the right Dharma. Thus, the person who slanders the right Dharma is involved in the gravest karmic evil.”
I think the passage quoted above says it all about the so called "exclusion" from the Eighteenth Vow. I would thou' add one thing: both sutras talk about slandering the true Dharma in the present moment: " the right Dharma is the Buddha-dharma. Such a foolish person has already slandered it; how can it be reasonable to think that he would aspire to be born in the Buddha-land?”.
A man offended Buddha really bad, throwing in his face with every kind of hard words, but the next day he felt sorry and asked for forgiveness. Going before him, he kneeled and asked forgiveness. Buddha said: "Get up, the person who stays now in front of me is not the same as the one offending me yesterday."