Well, if what the author of the op-ed is saying is true, they are one of the few people holding back the worst of Trump's behavior from destroying this country.
Unmasking that person will surely make them unable to continue doing so.
That assumes that the op-ed is completely true and that the strategy being described (resisting the worst impulses of a dangerously inept leader from inside the administration) is the correct one, but it's not a hard argument to make under those assumptions at least.