Long answer: As soon as a highly emotional topic is under discussion, humans feel like an attack on the idea is an attack upon themselves personally. Once that happens, their higher reasoning gets short-circuited and they begin defending "at all costs", including rationality. The more of an identity-belief it is, the harsher the response. They will say anything, even untrue or unfair things in order to "defeat" their attacker. Pointing out flaws in their reasoning only makes things worse. Bringing up evidence only strengthens their resolve (the backfire effect https://en.wikipedia.org/wiki/Belief_perseverance).
Engaging in a debate while emotions are flying is a fool's errand. Wait for things to calm down first.