Ok, I think a key moment in Anakin turning to the Dark Side is his reaction to his mother dying.
My first question is - who wouldn't do that?
If I were him, I would have sliced them up too. You kill my mother, you die. Simple as that.
My second question is - why exactly was his mother kidnapped? What were the Tuskans going to do with her? Make her a slave, hold her for ransom (doubtful), eat her? I don't know why they'd want her. Now, I can see why they'd want Padme.....
A common person would probably kill the men only, and you have to remember the Jedi arent meant to be common people, they are meant to show restraint. As for the reason why they kept Shmi alive, Im guessing it will be revealing ep 3 or it is just an overlooked detail. Maybe it was part of Sideous' plan?
jedi forgo and give up all love when they become jedi. killing a whole villiage just because your mother died is not logical and is on PURE emotion.. which again is something a jedi is not supposed to do.
emotions lead to the dark side, simple as that. clear headed logic and use of the force is what a jedi is all about.
as for just her mother being kidnapped.. they probably went for the whole farm but were fought off and only managed to take her.
I believe the kidnapping of Shmi was part of Sideous' plan as that is when Anikan started having the dreams and my guess is that Sideous knew Anikan would sense her tension. Why else would she have been kept alive for a month?
yah, i like that, sidious sends a messenger to the sand people saying there is a reward for shmi skywalker larrs , and she has to be alive to get the money, and then the sand people keep getting the message to hold her hostage and they will come by any time soon to pick her up and give them the money.
Anakin's mother dying is just the start of his turning to the Dark Side. It is drawn out process and not something that happens overnight.
Remember that Vader started the process for Luke in Cloud City when he tells him to release his anger because he (Vader) killed Luke's father. The call of the Dark Side continues ultimately to the point where Luke is on the precipice of holding his sabre to Vader's throat on the Death Star. If he kills Vader, his 'journey down the Dark path will be complete', if he doesn't then he has overcome the Dark Side and can consider himself a Jedi
I think the reason for Shmi being kept alive given in the novelisation is that the Tusken's are using her to determine information about humans. They're torturing her to see what the limits/weaknesses of her body are, presumably to give them an edge in future attacks.
They took her because she was an easy catch, they had been testing the limits of the security perimeters of Lars' farm in the nights beforehand and when Shmi went out to pick mushrooms from the vaporators one morning, as she did every morning, they snatched her on the way back home.