If it's what they want and you know this going in, then to work the job, you need to do what they want in that aspect. It's their place of business. I mean, if the beard is that important to you, you can always look for another job.

@CountScrofula if they ever ask you to shave your beard at work, you're quitting.

I guess you have to shave or not accept the job.

Shave or change jobs .. guess it depends on how good a job it is.

Shaved mine to wear a respirator and be on an Emergency Response team when I worked in a chemical plant early in my career. Re-grew it after I transferred to an office job at another site about 3 years later.

How badly do you want (or need) the job ? Consider that question and you have your answer.