The problem, in Josh's estimation, lies with people imposing what he calls "objective-prescriptive," moral beliefs on others, when doing so may be sub-optimal for them. If the essence of morality is goodness, then any sub-optimality may be immoral for the person imposed upon. His argument is about maximizing what is ideal for each person. Nothing matters but the maximal epitome of what's positive and ideal.
To be more precise, he calls his system inter subjective-predictive morality or ISPM for short. ISPM is about giving each person what is morally ideal for them based on what they want, based on fact, rather than offering generalizations about what is right for everyone or what everyone should do, even if it isn't evident. Provided they aren't hurting someone else, there is no self-evident justification from barring someone from their best end good or from living their most valuable life.
This type of logic, which imposes moral beliefs on others in an arbitrary and less than ideal way, is what he calls the virus. Josh posits that something called the application fallacy hinders all objective moral propositions because they fail to convincingly establish to whom moral rules apply. He argues that the statement "x is wrong," is in fact not a complete argument. We must establish who x is wrong for. If we say x is wrong for everyone, it is often not self-evident that it is wrong for everyone.
Interestingly, Josh's argument is just as much attack on subjective moral theories like post-modernism as it is on objective moral theories like virtue ethics and deontological ethics. Subjectivists tend to default to objective-prescriptive morality in practice in an extremely virulent way, even while declaring that there are no moral truths. ISPM differs from both in that it describes only, but does not dictate or impose. It is about seeking the ideal and not hurting people of forcing things on them.
My Stoic readers may be challenged, as i initially was, by the fact that ISPM tends to conflict with virtue ethics (which assumes certain virtues are optimal for everyone). However, I think it is possible to be a moral objectivist without imposing your morality on others in practice.
In dealing with others, Josh argues that we should not go beyond the mere annoyance of individuals via our behavior, as doing so is not maximally good. However if their intrinsicity involves directly hurting others, (they are a bully, a rapist, or a murderer), then we would be completely justified, in mooting that immediately.
When we make moral decisions and not all the variables are known, a level of risk of hurting someone is involved. Therefore having patience and mulling it over as long as is sufficiently maximally good, increases the chances of our mitigating these kinds of risks.
Overall I think Josh is onto something quite important in The Zombies, and I think largely his argument succeeds. My main criticism of the book is the occasional political aside which seems to undercut the main argument. I think these are included to appeal to his target audience - probably left-leaning thinkers - although in my estimation it naturally appeals to anyone who is non-authoritarian. Josh makes it quite clear (and I agree) that both the left and the right get a lot wrong in terms of trying to force their beliefs onto others.
I think that a necessary corollary of his argument is that some kind of non-impositional minarchist government would be ideal, since ISPM when implemented really necessitates small government, even direct democracy, in order to avoid violating each person's intrinsicity in the way Utilitarianism does (as many government actions are necessarily harmful to some.) I asked Josh about that, and much more, in our interesting YouTube chat, so please check it out for further details on the book.
Josh has made the book free and available to everyone as a digital download, even though it represents more than a decade's worth of work. Visit thezombiesbook.com to read it.