Except the example they use is climate change... some people claim that all the scientists are in on a conspiracy and that climate change isn't real.
You can't respond to this by saying "fine, we will each believe what we want and won't force anything on each other", because if climate change is real, we HAVE to take collective action to stop it.
This is the case for a lot of conspiracy theories... Covid, climate change, etc. There exist real problems in the world that requires everyone to take action. We can't just throw up our hands and do nothing just because some people refuse to believe reality.