Two people are debating the morality of a particular action. person a explains why he believes the action is wrong. person b disagrees with person a. her response to him is, "that's your opinion." did person b make a strong ethical argument?

No, he can say that's your opinion, but that is a weak ethical argument, he needs to say why he disagrees, and what are his view points on his reasoning, like why does he believe what he believes, just as person A does.

there is an explationation of this on a site called crash   course world history 1

the arab empire adopted the muslim religion as their main belief. arabs would influence the people from the territories they invaded towards islam (the muslim belief).

nevertheless, throughout the history of the arab empire, rulers brought intellectual individuals from other religions to their centers of learning. these other foreigners included jews, christians, greeks, persians, and indians.   these resulted in the adoption of important knowledge developed by these cultures by the arabic empire. for example, the works of aristotle were translated from greek to arab and indian scientists brought the numerical concept of "zero" to the arabs.

nowadays, 93% of the arab population is muslim, which at the same time is subdivided in sects including the sunni, zaini, alawi, shia. the remaining 7% is composed mainly of christians.