One way to help out a sceptic about something is by arguing that what she is sceptical about is way more widespread than she thinks. Of course, that's a risky strategy, since instead of her scepticism disappearing, she might just widen its scope. Here's one example of this risky strategy.
Authority sceptics are sceptical that another person's commands can generate obligations for us, except in certain unproblematic ways (a command from someone trustworthy might provide epistemic reason to think that the commanded action is independently obligatory; when one has reason to believe that others will follow the command, there might be reasons to coordinate one's activity with theirs; etc.). There is something seemingly magical about generating obligations for another just by commanding.
But isn't it equally magical that we can generate non-obligating reasons for another just by requesting, or obligating reasons for self just by promising? Yet it seems quite absurd to be a request or promise sceptic.