Why not?
I don't know the American system at all well, but I don't see how you can be forced to print anything that you disagree with using your own printing service.
If any potential customer insists that you use your own services and equipment to print fliers, documents, sheets, etc that has content you disagree with, then why should you not be able to refuse?
Is there a specific story you have in mind?
Mark
and I can and will make fliers for political candidates or causes, should I be permitted to pick and choose the candidates and causes that I will offer those services to? What set of rules, other than common sense, should govern who I must serve and who I can choose to exclude? Obviously I'm not going to accept a job from a foreign enemy advocating overthrow of our government so I'm not looking for the extremes.

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