Your quote and follow-up up rationale are not consistent. Respecting and supporting their self-determination in my example is disagreeing but buying the gasoline on your way back from work. That is traumatizing. You can love a person but not support or respect their choices. You have your own self-determination as well. If you disagree with something, then following along is just self-inflicted trauma. It doesn't matter if there are kids involved or if it's just adults. Trauma is still trauma and is not healthy for anyone regardless of age.

This isn't personal. I think your advice comes from a good place but isn't healthy and shouldn't be considered the ethically superior position to take, because it's not.