@dend08:
That is a different matter cause that bad guy did not honor the result of his fight with Wan Jia.
That guy lost a fair battle and as such should have accepted his loss against Wan Jia.
But he was a sore loser and tried to pull a self-destructing attack after losing.
Hence he showed disrespect towards his opponent.
Therefore he lost his right to be counted as "honorable" and a s such as a "man".
That is why samurai-boy cut him down.
For those ideal samurai honor is even more important than their life after all.