If a Philistine submitted to being tied up and circumcised by the enemy, they might have met their death at the hands of the Philistine leader, who would scream... "Are you weak... A coward? Then die like the dog you are."
Afterward, he would look around and ask, "Anyone else afraid to die in battle?"
With that, he and his army would do what these men have done for centuries... line up in battle formation, and rush the enemy with lances held high, and shields at their side... screaming as they advance.
That's the way of war, of ancient times.
There aren't many of that era, who did not think like this:
Death with Dignity is Better Than a Life of Humiliation.
Imam Hussein was the Imam of morality, humbleness and kindness and he wanted to guide the enemy army into the right path. He preferred death with dignity as opposed to life of humiliation for the revival of Islam.
Consider Samson. The Philistines captured Samson, blinded him, and then called a ceremony to make fun of him. They humiliated him, and sought to make him a laughing stock.
What Samson did, is what any warrior in those times would do. Samson dragged the building down on himself and the enemy... killing more in that one event than at any other time in his life.
This is the same the Philistines would do.
They would be willing to die, if they could kill David and his men, rather than allow David to humiliate them.