“Discerning” does often relate to the application of judgement. However, it’s important in applying judgement to be aware of cognitive biases that may predispose one to apply things like confirmation bias to one’s observations and interpretations.

But it is possible to be skeptical of something without challenging someone else to prove something to you. Indeed, a lot of people who are skeptical of controversial topics (such as climate change) describe themselves as “skeptics” (“non-believers” is one I’ve heard in this context as well) but in reality they tend not to be challenging an “opponent” to convince them – they don’t want to be convinced. In many cases, they’ve looked at the data and applied a personal bias to the interpretation of the data, and have invested themselves so heavily in their position that they’re extremely unlikely to feel safe in acknowledging they were incorrect.

Put another way, some people do tend to think of being skeptical about something as being a position that is not changeable – at least that’s been my experience.

In other instances, some consider a skeptical position to be one that is highly unlikely to change. Richard Dawkins’ skepticism about the existence of a deity or supernatural explanation for the universe or life comes to mind.