Technically, OP, you can sue him for harassment AND public insult. AND also get him fired (probably) from his company.
law.moj.gov.tw/eng/LawClass/LawA … e=D0080067
See Article 89.2
Also see this thread: Flipped the bird, charged under Taiwan's "public insult" law
You probably won’t get much from suing him though, unless the judge decides to fine based on the length of time and the number of times he insulted you.
Plus, you’ll probably make him an enemy for life.
But you know the saying, hurt people hurt other people. Maybe he had a seriously bad day dealing with a foreigner. Anyhow, that’s no excuse to stereotype all foreigners. His inability to contain his hostility is clearly a sign of mental issues. Who knows what such a mentally unstable person would do if he got really angry.
BTW, your Chinese is really good. 