What happened with Luke and Mara Jade is a perfect example to why Light-Siders can't Love.
When she died, he went out on a rage mode with Lumiya(If I remember correctly). Do you hear me? RAGE MODE!
Thats why PJO don't practice Love because losing it could turn you to the Dark-Side.
Luke isn't fully Light-Sided, when he gets ANGRY he sometimes will use a Dark-Side Ability. Samething with Kyle Katarn. But they will never use them at the same time. You can't be angry and Peaceful at the same time!
I suppose that this is true........... darnit. I guess my Luke analogy wasn't as great as I thought.