In fact, you are rewarding by all the extra exp points you will gain by slaughtering them (instead of buddying up with them). Most people go the templar route to make an easier go of it through the castle.Of course, you could play both sides, and become a templar in name and still whack them.
The only thing that is required, is to complete the ritual (if you need to get into AP and haven't planned ahead).
Tools for Wizardry(r) 7