Treat disabilities like you treat race, sexual orientation, sex, age, nationality, religion etc.

Why make your tenants have background checks if you're going to let them move in their boyfriends/girlfriends/friends who are violent offenders or sex offenders?

Her son who is the sex offender has a job for 1 year.

In my state, that would include things like court records, criminal convictions, sex offender registration, etc. 

All of the details were there; toenails, fingernails, nostrils, sex organs and so forth.

I think you owe your client - especially those who are new to real estate - the duty to help them find the house that is right for them, whether it be traditional sale,Unless you are voilating Fair Housing Laws (Descrimination based on: race, color, religion, sex, handicap, familial status, and national origin; blockbusting; steering), I don't see any legal obligation to show a property or obligation to do business with a potential client.

The tenant has been registered as a sex offender for 30 years. 

Honestly the guy being a racist would probably be the thing I paid the least attention to in this situation.But sex offenders, thieves and drug dealers don't tend to advertise that in front of their house.

Then under that, I have, "Conrad Rentals, LLC does not discriminate based on race, color, national origin, religion, sex, familial status (including children under the age of 18 living with parents or legal custodians, pregnant women, and people securing custody of children under the age of 18), and disability." 

Our stated criteria:Our Criteria:We do not deny housing for race, color, religion, sex, national origin, handicap, sexual orientation, marital status, or familial status.We do deny housing to individuals: when the application is not complete or accurate where there is no sufficient income/resources to pay rent and livewhere there is poor prior tenancy: evictions, violations, damage to rental property, poorly handled move outs, amounts are still owing to landlords or utilities.Criminal activity is at our discretion depending on severity, number of convictions, and how long ago.