On reflection, here's what may be a simpler (but less concrete and less precise) way of putting my point below:

1. Making statements that cause serious harm (for instance, because they embolden the enemy) is not itself immoral.

2. Making statements that you know will on balance cause more serious harm than good likely is at least presumptively immoral. (I'm not saying it should be legally punishable, only that it generally shouldn't be done.)

3. What are the main differences between 1 and 2?

a. Making statements that cause serious harm may be proper if you think they will on balance do more good than harm.

b. Making statements that you think will do more good than serious harm is generally not immoral (especially if your thinking isn't unreasonable), even if you prove to be mistaken.