The walkthrough is wrong, the best way to complete the quest is to be a devious little s*** =P
agree to help the Alik'r (so you don't have to waste time slaying 8 guys), lead Saadia to the stable then quickly run behind Kematu and go sneak, once Kematu stuns Saadia sneak attack him with your one hander (x6 dam) and finish him, after doing so the quest pops up "Speak to Saadia" tell her "The Alik'r won't bother you anymore, blah blah blah" she thanks you and is happy so gives you 500G then loot Kematu for a further 150G and two nice swords.
All and all, least trouble for max profit, plus you get to see the whole quest!
I would never betray the all mighty noble Redguards.