If somebody you know, are friendly with, or consider a close ally is accused of e.g. sexual harassment, plagiarism, or other scurrilous crimes, here are some things not to do if you’re invited to sign a petition in his/her defense.
— Don’t announce to the world that you know all the facts and evidence. You probably don’t, unless you are the accused or the plaintiff (and even then…).
— Don’t couch your petition in the mode “X is so brilliant and distinguished that s/he deserves special treatment unlike that meted out to ordinary mortals.” That won’t play well when the letter’s leaked.
— Even if you would probably say, on the street or in a bar, “I can’t believe X would do a thing like that!” do not write a letter in which you claim publicly that “The brilliant and distinguished X, whom I know extremely well, is incapable of such actions and therefore the accusations must be dismissed.”
— It would also be to your and the accused’s advantage not to try the tribalism move, i.e., “An attack on X is an attack on all who belong to our set (or: intellectual distinction in our age, all that is good and holy, etc.).” What if X turns out to be guilty? Then you’ve handed your entire tribe over to the hostiles (who may have no stake in the present accusation but will surely be glad for a chance to dunk their rivals in hot water).
— Above all, don’t attempt to blame the (professed) victim for causing the mess. It looks bad and may make you a co-conspirator in retaliation, should things come to that.
You may, I think, say how much you admire the person’s work, how vital his or her teaching is to an academic program, how deep your trust in him or her runs, how many times he or she has helped you with a problem– in other words, you can step up as a character witness. Not as a witness of fact unless you’ve observed facts. And don’t confuse character (ethos) with acts (praxis) unless you have a really ambitious theory of how the two intertwine. It’s easy to be taken the wrong way. A rule of thumb: if you would be outraged to read a letter if only it had been written in defense of a Republican, don’t sign it.