Please refer to the Notary Public Code of Professional Respsonsbility, Article A 1-a-4 Improper Refesual Due to Nonclient Status: Link here http://www.nationalnotary.org/UserImages/Notary_Code.pdf
The Notary shall not refuse to perform a lawful and proper notarial act solely because the signer is not a client or customer of the Notary or the Notary's Employer.
Another source is the National Notary Assocation. This was cut and pasted from their website
Can a Notary refuse to serve people?
Only if the Notary is uncertain of a signer's identity, willingness, mental awareness, or has cause to suspect fraud. Notaries may not refuse service on the basis of race, religion, nationality, lifestyle, or because the person is not a client or customer.
As long as the request is a legal one and the person has proper identification, you are a public servant. Now if the id you are presented appears to be altered or the signer does not appear willing to provide you the infomration, you have grounds for refusal. I am sure your employer who become more upset with discrimination lawsuit than you performing your duty of witnessing a signature for a person who you identified as matching the id.
By the way, I was named in a lawsuit ( in error) by one of my clients whom I performed a notary for on a real estate transaction. Since they were a customer of my bank, I performed the notary. The bank since the document was not one of theirs were not named in the lawsuit and was not required to provide me a lawyer. Things to think about.