I would like to clarify that this quote is not my statement: I am not stating that the first sin was a more abhorrent deed than the subsequent sins.
What I state is the following:
Before the first sin there are NO human sinners.
After the first sin there are human sinners, and thus, before any subsequent sin (any other sin after the first one) there are human sinners.
Consequently:
After the first sin God has to decide how to treat the sinners.
After any subsequent sin, God has no longer to decide how to treat the sinners, because he has already decided.
To this extent my statement seems a matter of pure logic!
Further:
Evidence proves that God decided not to condemn the sinners to hell immediately after sinning, but let the first sinner and subsequent sinners like us on earth.
Why?
The reasonable (in my view obvious) answer is:
God is merciful and let us sinners on earth to give us time and opportunity to repent and reach salvation.
This logical answer is largely confirmed by scriptural text, specially by the teaching of Jesus Christ.
But then: Would it have been sound on the part of God to let sinners on earth as if they had not sinned?
The reasonable answer to this question seems to be:
No, this had moved the sinners to sin more and more and so supported rather their damnation than their salvation, against the very aim for which God let the sinners on earth.
This (in my view also obvious) answer is largely supported by scriptural text too.
Accordingly, after the first sin God let us sinners on earth in the state described in Genesis 3. This is the so called “state of original sin”, where in lack of God’s original grace we are submitted to illness, death, and concupiscence. Thereby we can better avoid the delusion that we are like God, feel the need of God’s grace and redemption, and move to ask God for forgiveness.