My argument against the use of these terms is simple and straighforward. A phobia, by definition, is an irrational fear. (Every phobia is a fear, but not every fear is a phobia, because not every fear is irrational.) Therefore, one who calls a critic of the doctrines of Islam or of the practices of its adherents an Islamophobe is implying that the critic is in the grip of an irrational fear, and therefore irrational. This amounts to a refusal to confront and engage the content of his assertions and arguments.
This is not to say that there are no people with an irrational fear of Muslims or of Islam. But by the same token there are people with an irrational fear of firearms.
Suppose a defender of gun rights were to label anyone and everyone a hoplophobe who in any way argues for more gun control. Would you, dear liberal, object? I am sure you would. You would point out that a phobia is an irrational fear, and that your fear is quite rational. You would say that you fear the consequences of more and more guns in the hands of more and more people, some of them mentally unstable, some of them criminally inclined, some of them just careless.
You, dear liberal, would insist that your claims and arguments deserve to be confronted and engaged and not dismissed. You would be offended if a conservative or a libertarian were to dismiss you as a hoplophobe thereby implying that you are beneath the level of rational discourse.
So now, dear liberal, you perhaps understand why you ought to avoid 'Islamophobia' and its variants except in those few instances where they are legitimately applied.