> Plus, don't underestimate the impact of forcing people to acknowledge that there is exactly one right answer and that it can be proven.

There's plenty of classes in a civil engineering degree to instill that particular lesson. Why does it have to be calculus? It's just legacy - it used to be that limits and integrals could only be computed by hand, so any aspiring engineer would have to practice that skill a lot. Now computers can do the tricky algebra on their own (and I'm not even mentioning numerical approaches, which are more broadly useful but can be very tricky in their own way), yet the calculus courses have barely changed.