It's easy to not consider ROI when one's talking about investment with non-negative gains strictly under your control. If you have money to spare, making your devices accessible will not reduce your profits, and there's a chance it'll increase them.
OTOH, pissing off China could mean huge losses for Apple, and that makes it a different story altogether.
Exactly. Even if Cook stands up for his (or our) ideals, the pressure China is going to apply to Apple will result in Cook getting ousted by the board, replaced by a favorable "Cook".
Companies (for profit or not) answer to their major stockholders. Even politics in a (democratic) country (EU or U.S. or X, place possibly your country where X) follow a similar mechanism: politicians conform with the wishes of the major coalitions that will keep them in power. Sure one can leave footprints of their ideals, but after some threshold they are intrinsically bound by their power base (usually lobbying).
I think the point many people are making is that "I will be replaced by someone willing to do this morally reprehensible job" is not an excuse for doing the job yourself, as that 1) increases the pool of people who are willing to do the job and allows more bad things to happen and 2) as people are not purely replaceable, it isn't clear that the Board of Apple will be in a good place to find someone as competent at supply chains as Tim Cook to replace him... particularly someone who is both competent and willing to play with China.
OTOH, pissing off China could mean huge losses for Apple, and that makes it a different story altogether.