One ethical tool is "What would happen if everyone did [action/behaviour]?"

What would happen if every lawyer refused to defend private individuals accused of eg murder? Innocent people would go to jail and/or guilty people would go unpunished.

What would happen if every lawyer refused to work for Shell etc to let them have new oil rigs and new gas rigs and new coal mines? Climate change would slow down [or at least stop speeding up] and there would be less deaths from floods in Pakistan and less deaths from wildfires in California and less deaths from heatwaves and...