My beardies have puffed their beard out, not for defense, but instead they puffed it out and it back in and they repeated this process a several times.
I have seen my larger one puff out in defense but this time it puffed out in a nice calm manner, i don't know why, its almost as if it was strecthing it or spreading it.
I think it is them stretching. When my boys wake up in the mornings both of them puff their beards a bunch and open their mouths really wide. lol They'll also do it when they're outside or running around the house.