I believe the comparisons between how engineering is practiced make this more than "silly". The purpose of the writing is not to answer that shallow question, but to better understand both fields.
When OP said that we are not 'real' engineers because we have not built a bridge is when I stopped reading. For how could anyone take him seriously after that?
'Real' engineers are not judged by whether or not they can build a bridge as if it's some rite of passage to being a real engineer. That's ridiculous on the face of it.
That he used this example as some kind of proof to justify his argument is where he lost me.
This was in reference to a quote from a software developer comparing software development to building a bridge. That is why "he has never built a bridge" was emphasized.