What is an example of a deductively valid argument for ethical relativism that appeals to tolerance?

Relativism and tolerance are closely linked, and often arise in situations of religious and cultural difference. Relativism refers to the idea that one must take into account the belief system by which people make decisions about practices that may be unacceptable to those of other cultures. Tolerance refers to not taking action to prevent others from acting according to their beliefs; it is usually but not always based on a relativist perspective. Other motivations for tolerance can include legal and political bases of civil rights in a given country or other jurisdiction.
Two cases that might work well for the type of argument you consider are eating meat and genital mutilation.
In many belief systems, it is considered wrong to eat meat. While there are different reasons, many people object to killing other animals because they respect their fellow creatures as living, sentient beings. For many, killing animals is especially heinous when done for the purpose of consuming their flesh. People who have these beliefs may consider flesh-eaters’ choices through a relativist perspective and tolerate their behaviors. That is, a vegetarian might consider that other belief systems do not place equal value on all living creatures. It may be neither possible nor advisable to try to persuade or prohibit everyone from eating animals.
Genital mutilation, or circumcision, is widely practiced in many cultures. These practices include male infant penile circumcision and female genital cutting. Opponents argue that subjecting children to any surgical procedure is inhumane because the children do not freely choose to participate. Proponents who argue for a relativist view point out that religious practices are a matter of personal concern and that parents are capable of making choices on behalf of their children.