TLDR; Presenting facts and evidence in an argument can further solidify one's beliefs rather than helping them change their minds.
Have you ever been debated with someone who actually changed their mind on the spot? That almost never happens. It turns out that presenting good arguments against someone's beliefs can often have the opposite effect of convincing them to change their mind. It can actually solidify their position even more!
This wouldn't seem to make sense, but it's worth considering what's going on in our brains when this happens. When a person is confronted with an argument that is incompatible with their existing beliefs, it causes cognitive dissonance which can cause an extreme amount of discomfort. We're wired in a way that prefers psychological consistency, but shifting belief is too difficult. Instead of maintaining cognitive dissonance, we tend to dismiss the new evidence, or even just double down on the belief in such a way as to cancel out the evidence.
The backfire effect almost makes it sound like it's futile to even debate with a person at all. For deeply held and strongly emotional beliefs, this may be true. It's difficult not to be frustrated by this bias. The trick is to go into these discussions with low expectations for actually changing someone's mind on the spot. Instead, endeavor to chip away at the boulder. Maybe plant some seeds of doubt, but don't push too hard. Put a rock in their shoes for them to discover later when they can fully introspect.