It’s a great question Andre. Personally, I think that having expertise is key for numerous reasons: not only credibility and correctness with respect to humanity’s body of knowledge, but also as a prerequisite to an expert feeling comfortable and confident on speaking to an issue.
It can be tricky in academia to define expertise. Our greatest experts are intimately aware of the limits of their knowledge, and are surrounded by colleagues they view as possibly more expert. And yet, academics are usually not surrounded by the public at large, and can quickly forget just how little expertise the public has on most matters.
I don’t know how to draw a fine line on engagement yet. It requires considerable discretion to decide when to leap in. That in itself is a deterrent to contribute, but it shouldn’t be.