@MissMermaid When I was searching on the Discourse Meta website about this topic, I found some posts about just this question from one of our forum’s previous moderators @BarbieBF back in 2015. It’s in the Discourse topic I posted above (@BarbieBF posted as Barbie on the Discourse Meta site).
it looks like Discourse has implemented this option in 2016 as something the site administrator can implement through site Admin settings.
Perhaps @SzAdmin might consider implementing this option (only allowing profile views if user is logged in)?