Ok - a couple of thoughts. First, no - don't call a lawyer. The providers aren't being discriminatory, they're simply declining to see you. A doctor can do that. So you don't have a case if you want to claim discrimination.
Second - why are you telling them that you want to have a home birth? It doesn't change the care they'll be giving you during your third trimester, so why do they need to know? I understand that you want to be honest, but there's no reason to even bring it up... especially since in the event of an emergency, you WOULD use their services.
I say this as someone who planned for a home waterbirth and ended up with an emergency C-section at the advice of my awesome midwife who realized that it would provide the best outcome for my daughter. She drove with us to the hospital and stayed the entire time. Not the birth I wanted or planned for, but it couldn't be helped.