Avira,
I don’t have direct references other than the above mentioned Rav, who had a senior public position in the overall observant community at the time. I don’t think I need to ask further, as this is pure Daas Torah here – first person from a teacher linking to the Gemorah we were learning.
I didn’t understand that the reason was “parnosa”, that is one would lose a job without learning hilchos nochrim. It is because one will be exposed to those people and (a) need to know enough to protect himself, (b) needs to know what to answer to both non-Jews and Jews he will encounter.
So, it is not “forced”, it is just something one needs to know n certain circumstances. You are gonna to be a shochet, you learn cow biology. Gonna to be a professor, learn how to deal with those problems.
In related news, R Steinsaltz was not shy to (occasionally) demonstrate his knowledge of secular history and literature for no other reason than simply increase rapport with students with a good joke. Although, he also signed when mentioning his meetings with senior non-Jewish clergy, saying that he had too much of that.
As to the shock, these were undergrads from MO NYC schools. They were stunned that halakha is not a look-up thing but requires analyzing personality. In general, the Rav told me (when I asked) that his main effort with these kids is to show them that Yiddishkeit deals with difficult issues sometimes and requires thinking. He did not need this effort with non-O kids who would be excited to ponder issues to begin with.