Ask them if there’s anything Biden could do to make them not vote for him. Just a yes/ no, don’t ask them for their specific red line.
If the say no- ask them how that makes them any different from Trump voters (they criticize his voters for following him blindly and the worst thing that can happen to them is being compared to a Trump voter.)
If they say yes; then it’s just degrees of difference from you and them.
Just finished it a few weeks ago. A Really sweet show. Teared up during the Pacific Ocean part