If FizzBuzzCorp is in the business of building CMSs in PHP, and Bob believes that there is nothing unethical about the diamond business, those two things are far apart enough that you can reasonably trust Bob's opinions on the diamond trade to not influence his decisions as a leader. Even if you think the diamond business is the most awful thing ever, it's extremely unlikely that that Bob's views on the matter will influence the writing of PHP websites, and you can probably overlook it as an employee/customer/investor in FizzBuzzCorp (unless the diamond trade is something you feel really strongly about).

However, every company deals with human beings by nature, and implicitly takes a role in social progress just by virtue of being a part of society.

If Bob has certain beliefs about the nature of the rights that should be afforded to some humans but not others based on things like their gender (or race, or sexual orientation, or other), then the probability that those beliefs will interact with his decisions during his tenure as a leader is pretty high.