3. Be a happy, kind, loving, and positive activist role model. Nobody wants to dine with Debbie Downer. People want to be happy, so they want to be around people that are happy, and they want to be like people who are happy. Doing your best to be happy and positive - even if you just fake it till you make it - will have people be more likely to come to you, trust you, emulate you, ask you your opinion, listen to you than if you angrily tell them what to do. And if they don't, then what? You got happier either way.
4. Breathe. And be grateful. If some really awful things are coming out of people's mouths, or if you're upset about the carcass being joyfully carved up on the table, practice taking deep breaths in through the nose and out through the nose. Consider each breath your attempt to dig deeper into your well of compassion and to be able to shower those around you with love, regardless of their views. Practice gratitude. You are with people who love and care about you, and who you on some level love or care about. Or did at one time. Or maybe you're with people you just met. They are doing the best they can in the life circumstances they have lived. They are unaware of their privilege and now is not the time to teach them. And you have food on your plate, electricity and internet, people who want to spend their holiday with you, a place to sleep, clean drinking water, and a toilet. Which is more than billions of other people have. Breathe and give thanks for the privilege of getting upset at the dinner table because of someone disagreeing with you. Give thanks that you are alive.