Really, none of this is that complicated. In the end, the postmodernists are correct: no one can decide for any other being maters of truth.

If one perceives oneself to be experiencing a material existence within a material realm that is external to oneself and that it can have impacts on oneself, for the sake of self-preservation, much less flourishing within that existence, one must seek to understand the sources and the effects of those impacts. If one perceives that there are other beings like oneself, one can seek to cooperate with them for the sake of greater understanding of that material realm and better outcomes within it.

If one’s perceptions include the observation that all such beings have no choice but to effect choices, one must accept that a normative condition attaches to that existence: recognizing those beings’ ‘fellowness’ by respecting everyone’s capacity to choose for oneself, beginning with choosing whether/how/to what extent to be involved in the process whenever any choice is being effected: mutual respect in effecting choices. That is what the ethic governing all relations among all such beings must be.