The problem is that you're not addressing 'adults with indecent behavior.' And even then, what is 'indecent behavior?' Pissing on a wall when you're drunk? Are you really and truly afraid of that person molesting your child? If so then you have serious issues...
> I hope to know about it. I don't care how minuscule the crime is, the possibility of repeat offenses or misbehavior is too high to risk it.
This right here says that you're not concerned with 'is the punishment too harsh.' "I don't care how minuscule the crime is," says that you don't give a shit about people that were too harshly punished. You would rather just brand people as 'good' or 'bad' and then avoid the 'bad' people. Sorry, but the world doesn't work that way. There are many shades of gray.
> any inappropriate behavior around children (impressionable, gullible, naive) should be punished.
The problem is that 'inappropriate' is subjective too. You're saying that the harshness of the punishment is subjective, so it can be ignored, but the 'inappropriateness' of the crime is paramount... only that's also a subjective measure.
> If a person shows that kind of poor judgment they should suffer the consequences of their actions.
So a person that pissed on a wall should have all of society treat him exactly the same as a person that spent a lifetime raping 7 year olds. Not only that, but someone that was 18 and had sex with someone that was 17 years old should be treated the same as someone that kidnaps 12 year olds and tortures them to death... You're a pretty vicious person.
{edit} Just to add, that someone that was convicted of raping a woman isn't necessarily a 'danger' to your child either. Even the people that 'deserve' to be on the sex offender list aren't necessarily all there for the same reason. {/edit}