[Landlord US - OK] Legality of limiting commercial tenants

We've got a three-person LLC and among our small bundle of properties, we have a commercial location. I took a call about it today from a prospective tenant who sounded very interested. She mentioned she runs a psychic business, doing readings and selling associated merchandise.

I didn't have a problem renting to her, but both of my partners do, for religious reasons.

I don't want to make this a religious debate.

I disagree with them on that issue, but that's not my question. I want to know what our legal limitations and responsibilities are with regard to potential discrimination issues. They want to refuse to lease to "immoral" businesses (which we haven't defined) but not, for example, a gay person running an insurance agency. (I'm not suggesting gay people are immoral, but my partners would.)

I've checked Oklahoma landlord-tenant laws and don't see anything there. It's my understanding that federal non-discrimination laws just cover housing. Is that a correct understanding? I know people can sue for any reason these days, and often do, but I'm more concerned about state or federal issues.