I feel that language as a job requirement is reasonable enough, since it's basically a skill. If the job requirements ask for job applicants of a particular race, then that will be harder to justify.
Exactly, It is one way of making sure that the majority of the applicants applying for the position of the race you seek. There is already overt discrimination against candidates over 40 - something the government is trying to rectify. So it isn't a stretch to figure out that covert racial discrimination is also occuring/has occurred - you cannot control/police this w/o strict rules/policies.
In other countries, some more multi-cultural as ours (i.e. whose citizens that are of many different races, religions and from different countries), the only language requirement is English (or the first language of that country) and there are anti-discrimination laws that protect against practices like these.
I've seen quite a number of positions where Mandarin is not necessary, yet the requirement is for the candidate to read, speak and write Chinese.
The ability to speak Mandarin is not an advantage when doing business in China as many an Sgrean expat in China has found. The requirement goes further than that - they also expect you to know their culture/beliefs - something many Sgreans who go there, are ignorant of.
Many Europeans, Indians, et al and their companies are successfully wheeling and dealing with the Chinese w/o having the ability to speak the language.