The intent was for this to update only the fields that are NULL, but it updates them regardless of their value or lack thereof. I did not want to change a value if it already existed; only if the field was NULL.
It's not a big deal, this will alway keep the field "correct" but I was curious why it didn't work as intended. I may need the intended behavior at some time.
SET Program = Employers.Program
FROM JobTitles INNER JOIN Employers
ON JobTitles.keyEmployerID = Employers.keyEmployerID
WHERE JobTitles.Program IS NULL