When going to a job interview, if a person suspects for whatever reason, that he may be unfairly discriminated against if he wears a yarmulka, is he allowed to omit wearing it? Would this be considered genevas daas?
Interesting. I don't recall ever seeing this question raised when the poskim talk about not wearing a kippa, which would lead one to say it is not a problem.
There are a couple of points to consider. First of all this would be what we call the viewer tricking himself, which is muttar. By that I mean the boss made an assumption on his own volition without the worker saying a word. Much like a homeowner opening a barrel of wine before his guest and the guest thinks it was done in his honor when in reality the homeowner needed to open it anyways. The gemara says this is muttar. As long as no steps are taken to trick the one observing such as dying the hair of an old slave to make him look young. The gemara says that is assur. See here for some points http://torah.org/advanced/business-halacha/5757/vol2no30.html
Here in your case there is also a loophole. If the bossman doesn't want a religious worker, and he thinks that not wearing a kippa makes this worker nonreligious, than he in fact got the exact worker he wanted. Someone he considers irreligious.
From the discussion of Rav Aviner it would seem that wearing a kippah at all times is an obligation. He discusses possible dispensation for a life-threatening situation, but the implication is that otherwise it would be forbidden to omit it.
A Kippah is an absolute obligation. A Kippah is of great importance. Our Sages explain that a Kippah is meant to instill fear of Hashem within us and is a sign that the Master of the Universe is above us (Shabbat 156b. Kitzur Shulchan Aruch 3:6). According to the Achronim, it is even more of an obligation in our times, since wearing a Kippah has been accepted by Torah observant people (Shut Meharshal #72. Shulchan Aruch Ha-Rav 2:6 based on accepted Jewish practice. And some say not wearing a Kippah is imitating non-Jewish practice. Shut Chatam Sofer, Choshen Mishpat #191).