I would argue that globalization can help lead to ethical relativism, but it does not have to.
Globalization can lead to ethical relativism because people get exposed to the ideas of many cultures. In the days before globalization, it was much easier to think that your own ways were the only proper ways. In addition, when countries like China were "backwards" it was easy to dismiss their ways as stupid and not worth paying attention to. Now that more and more countries are becoming economically important, it is harder to dismiss their cultures and values.
However, globalization does not have to lead to relativism. Just because you find out that other people are different does not mean that you have to accept their values. You can learn about others' values but still feel that there is one true set of ethics that should govern all people.