Because he is allowed to be pessimistic as a military adviser he is being pessimistic as a recruiting sergeant.

Just in the same way the pessimist (who is the cosmic anti-patriot) uses the freedom that life allows to her counsellors to lure away the people from her flag.

Granted that he states only facts, it is still essential to know what are his emotions, what is his motive.

It may be that twelve hundred men in Tottenham are down with smallpox; but we want to know whether this is stated by some great philosopher who wants to curse the gods, or only by some common clergyman who wants to help the men.
The evil of the pessimist is, then, not that he chastises gods and men, but that he does not love what he chastises--he has not this primary and supernatural loyalty to things.

What is the evil of the man commonly called an optimist?
Obviously, it is felt that the optimist, wishing to defend the honour of this world, will defend the indefensible.