What I learned as a hired consultant to autodidact physicists
Whenever I talk about physics (to non-scientists), I notice that people have a tendency to start veering away from the math and onto irrelevant metaphysical tangents.  For instance, I'll be trying to explain the history of renormalization in quantum field theory, and someone will suggest, "Well maybe we don't really understand infinity".  No, we understand "infinity" just fine.  It's a concept that's clearly defined using a set of axioms that have been around for thousands of years.  "Well maybe the mathematicians are wrong."  I start losing my patience pretty quickly at this point.  The other big one that annoys me is "Well it's just a theory".  Sure, and gravity is just a theory too.  If you doubt it, you're free to go skydiving without a parachute, but personally, I'm not taking any chances.