How to talk to family about spanking

My husband and I were both spanked as kids. We have family members who cuss at their kids....a lot. We don’t judge others for what they choose to do and won’t tell anyone how to raise their children. However, we don’t want to spank our daughter. We have some family members who think we’re dumb and need to spank our child and if she’s “bad” then they’ll spank her. I do NOT want our family members spanking our daughter either or using foul language to get a point across to her. How do I have this conversation with them?! What do I do if they say they think it’s okay so they’ll do it anyways?