In some cases no, we shouldn't even stand in the way of sinners. In ignoring their decision we are offending some of them. There is however something we can doI'm not sure I totally am understanding.
If we talk to somebody about becoming a Christian and they say they don't want it. We are not supposed to talk with them anymore about it??
I understand how you feel BUT---I'm not sure I agree so much with this.
I agree we should pray for them. That will help. But I hate to turn my back on someone and allow them to swirl down hill.