It is perfectly OK for an individual to show bravery - which, as you said, is acting without regard for one's own self-interest, usually for the benefit of others. If your actions are disregarding others' self-interest, then that is not bravery, but recklessness. And making personal decisions for other people from a standpoint of authority, whatever the reason, is something approaching abuse.
It has nothing to do with authority.
On your view, it's not only wrong for the Borders' CEO to stand up to the Islamists, it is wrong for ANYBODY in Borders', including the lowliest store clerk, to offer for sale the "offensive" material without permission from ALL THE OTHER WORKERS IN ALL THE OTHER STORES: since if the Islamists hear someone disobeyed them at Borders', they won't bother to track them down individually, but will bomb any Borders' store they can find.
Conclusion: If someone threathens only you, or a small group of people, then bravery might be permitted. But if someone (like the terrorists) threathen random or widespread violence, the only "non-reckless", "morally permissible", action in reply is cowardly capitulation.
Does this make any moral sense to you?
Let us take another example. There were jews in WWII who were hidden by Polish peasants, despite the fact that the Germans threathened to kill the families of those who hide jews. On your view, if the Germans had some limits on their behavior and only threathened only the person who actually hid the jews, hiding the jews would have been brave. But since they were ruthless enough to threathen to kill the families as well, the peasant hiding the jew in the cellar was no longer brave, but a morally reprehensible reckless fool.
Same goes with the reckless fools in the French resistance (the Germans theathened, and sometimes committed, mass reprisals against innocents in retaliation for their actions), the reckless fools in the American war of independence (many Americans were loyalists and didn't want war), the reckless fools in...
...well, you get the idea.
Does this make any moral sense to you?