Where did he get that attitude, she wonders?
From playing MMPORPGs in a previous life; he recognizes their type, and knows that they aren't going to give them a chance.
They can attempt to evade, but these guys won't give up on their hunt until one or the other party is dead.
Thus, no mercy can be extended, for none would be granted unto them, and these types would consider anyone who gave them mercy fools.
This isn't a game, and there are no respawns once killed.
Dead is dead, so if someone plans to kill you, you have to consider the consequences of letting them live in regard to their remaining a threat.
Clearly, Rosetta doesn't have that much practical experience of adventuring.
I must say, the physical appearance of the baddies is oh so stereotypical.