One of my favorites amongst Sandman’s advice on outrage management is his page on hostile meetings. If you are the public face of a say the local landfill this is for you.
But for all of us, there is valuable counsel here on how to deal with people who are hostile to an idea that you think is important. I will summarize with Peter’s heading “Memorize this hierarchy: listening → validating → responding → rebutting”.
Another way: let them vent until they are out of steam. Empathize. Respond.