Prof. Fish distinguishes between a moral judgement and a professional one. In the case of the boycott, he chooses the latter.
Let’s see, how valid this approach is? Suppose an electrician is called to wire circuits for the installation of an electric chair. Said electrician can blithely offer his professional opinion on the wiring job, keeping moral questions of capital punishment and questions of death by electrocution out of his calculus, and get the job done without bothering his conscience. Or, he can raise the moral issues about capital punishment which might impair his willingness to take on the wiring job.
But what he can’t do in good conscience is use his professional judgment about the work to cover for his unwillingness to face the moral issues inherit in the job. That seems to me what Prof. Fish has done in the dealing with the boycott issue.