Because you didn't now that sunry actually killed her. Or have any valid evidence. So in your eyes, his still could be innocent. Wait, I thought you said "Why wouldn't you GET dark side points," not want. Sorry.
You could get the right answer by NOT looking at the tape at all. Then, you prove Sunry innocent, which causes problems for the sith. You also do not get any dark side ponts.
You could try to redeem them!
I don't think any sith would go back to the light at this particular time. I mean there about to conquer the galaxy! Why would they join the losing side?
Anyway welcome to the boards Yoda. Heres a tip, these boards can be brutal and you may want to refrain from posting similar threads in the future.
Cheers!
And one more thing Yoda. Beware of Hades One. His bad attitude and immature complaints are a thing to be avoided. Take with you our words of wisdom for you can only rely them.