A few years back I did some extensive research in the area of US Constitutional/Federal law prohibiting discrimination in the workplace based on religion. Here is the bottom line. It is next to impossible to win a case claiming religious discrimination if an employee or prospective employee knew at the time he/she is hired of a written company policy that prohibits specific religious attire or symbols or that prohibits specific practices (such as refusing to work on a particular day like Friday, Saturday or Sunday).
Now the article says this: Sikh Coalition, whose attorneys have been in touch with Tri-County Lexus, said the company denies having any such corporate discriminatory policy.
In this case everything depends on whether the company can produce a policy that forbids facial hair.