I don't have the privileged information to know if it is true, but this feels more like a gut reaction then a cost benefit analysis action. Musk is known to be pretty polarized in his tech ethics opinions.
Cambridge Analytica isn't the first incidence where Facebook was used for political purposes. Obama Campaign Manager Jim Messina explains their use of it in 2013:
https://youtu.be/mZmcyHpG31A