I am with you 100 percent
One offense is sufficient, in my view, to separate the offender from the rest of us, permanently.
However, our legal system MUST start to make the relevant distinctions before we do this. A statute must distinguish the 18-year old boy with the 15-year old girlfriend from the child rapist.
Most states now do not seem capable of doing this, and until they are, I'd hesitate about changing the penalty.