Maybe they operate by the same temporal guidelines the Doc does?It should have gone back a few hours and said "Look, zap the one-eyed tentacle weirdo. The Doctor is coming through that door in five minutes so zap him too". We could have had a fun time-shifting episode that leaves the universe in a nasty tangled knot.
Not to interfere with their own time stream, ect.
Its a feable excuse to a universal bond-villian style problem, but I think they were trying to infer its also in the Dalek programing to explain themselfs.Less talking to your victims, just zap them and be done with it. Shoot first, scream "EXTERMINATE!" after.
Much like the Borg dont mind you wondering all over their ship.
A Dalek purhapes dosnt mind explaining themselfs because despite all logic, they still cant quite belief you are a threat.






