The status of an office in terms of mezuzah is a matter of halachic controversy. Indeed, many authorities rule that it only needs a mezuzah if the owner or renter lives in the office day and night.[1] It is also not a storage area because even if it has a desk, a telephone, a computer and a file cabinet, these are there to facilitate the work; the office is not there to store them.[2]
However, other authorities argue that modern offices cannot be compared to the temporary market booths exempted by the Talmud, as people spend most of the day in our offices on a constant basis.[3] Indeed the custom is to affix mezuzot on Jewish owned or rented offices, albeit without a berachah.[4]
That being said, the obligation to put up a mezuzah falls on the owner or renter of the office and not on you.[5] Since your employer could easily move you at any time to another room, he has not allocated your office to you in a way that can be construed as a rental.[6] As such, you do not have a religious responsibility to affix a mezuzah on your employer’s door, and you definitely can continue to work in your office, even if he will not allow you to affix a mezuzah.
In addition, your employer’s judgement that placing the mezuzah would cause material damage to his business, whether correct or incorrect, would entitle him to rely on the lenient opinion in this matter.[7] His refusal to allow you to do so cannot be construed as an assault on your freedom.
This consideration alone would also exempt you from reproving him any further.[8]
[1] Turei Zahav 286:11; Chayei Adam15:11.
[2] Agur B’ohalecha 34:44:83, citing Minchas Yitzchak 4:89:5. If the office has a special room allocated for files or large equipment, it would be obligated like a storage unit (see question “Self-Storage Units”).
[3] Perishah 286:22; Chidushei R. Akiva Eiger Y.D. 286:11; Aruch HaShulchan 286:26.
[4] Minchas Yitzchak 2:83:4; Chovas HaDar 3:8:24.
[5] Minchas Yitzchak 2:83:4.
[6] See Shevet HaLevi 2:156.
[7] See Rema O.C. 656:1 and Mishnah Berurah, op. cit.
[8] Minchas Yitzchak 2:83:4.