I say speak out, confidently and directly. You don't need to (and shouldn't) criticize the carbon footprint of the people present. Focus on the BIG climate criminals—billionaire oil profiteers, oil companies and their executives, politicians purchased by oil profiteers via their lobbyists. WE need to put an uncomfortable spotlight on these criminals, disobey them, ridicule them and NEVER STOP.
Once THIS becomes the conversations—through your stubbornness and mine—we are on our way to the change we need...if our children and our biosphere is to survive.