No, banning contact between sex offenders and women does not violate the constitutional rights of sex offenders. Banning sex offenders from approaching women helps to protect women that are at risk, and does not count as what the constitution considers "cruel and unusual punishment." These criminals gave up their right to approach women when they perpetrated their crimes.
When a person commits a crime, they give up certain rights. Sometimes that means giving up their freedom and making the person go to jail. Other times, it means the person is still allowed to be free, but they can't do certain things. This is called probation. There is nothing wrong with using probation to protect the public.
Why should more women be exposed to a known sex offender? There are enough unknown dangers facing women as it is, why do we need to go out of our way to add one more? If a person is guilty of a sex offence, they should be monitored. Giving them rights may result in destroying another person's life.
No, banning behavior does not violate constitutional rights of sex offenders. Sex offenders are criminal and as such have forfeited many of their rights. Banned behavior is part of their punishment and an effort to prevent further offenses. It is really a form of probation and provides the offender more freedom than a prison sentence would.