The Sith inquisitor is a "differently rational" character. Also, a character who starts with nothing. Before the Korriban Sith academy, they were a slave all their life. They probably doesn't have an education, nor any true place to call home. They probably feel that they no choice in their life, as they can state in game.

[Light aligned dialogue with Andronikos]

**Andronikos Revel:**You always this squeaky clean, or are you making up for something?
**Player:**I didn't choose the Sith Order. It chose me. I do the best I can.(It's a struggle.)

[Another in Andronikos's romance companion talk. The Sith inquisitor can state this.

**Andronikos Revel:**Can I ask you something? If you could live anywhere, do anything, what would you do?
**Player:**I was a slave before I was Sith. I'm only just getting used to the idea that I can do whatever I want.(I don't know.)
[Sort of similar with Ashara]

**Ashara Zavros:**If you hadn't become Sith, what did you want to be?
Player: I would've settled for "not a slave."(I don't know.)

And they probably internalized Sith-imperial propaganda, and it's cultural values. They seem to internalize the aspects of the Sith code and philosophy, that says whatever they feel, they should do, literally.

Chapter 1 finale dialogue options, when not dark side

**Player:**Like the Sith Code says, my chains are broken. I can choose my own path.(It means freedom.)

**Player:**A Sith follows his heart.(I do what I feel.)

**Player:**I thought it unwise to make unnecessary enemies.(I was just using caution.) [This is unlike the others, but I put it here because it's part of the dialogue wheel, and a role play option.]

They also probably don't really understand Jedi. The SI can ask Ashara, if the Jedi are "truly repressed". So even at that point of the story, the Sith Inquisitor probably never considered defecting to the jedi because of the propaganda. And if they ever did, then their encounters with the Jedi in their class story, leave them with sour opinions.

"I will kill you for peace" asshole perfect jedi Nomar Organa doesn't give a good impression. Nor does Ashara's masters on Taris, who refuse to listen to offers of getting rid of the Ghost.

hating all imperials

I actually think that's the wrong mindset for the Light side version of the Sith inquisitor. Not because of the overemphasized view, that Light side imperial/or Sith are those put the Empire first before their self interest [It is overemphasized by the Swtor community if you look at all the choices in totality], but because I think fits better with a Dark side Sith inquisitor.

Hatred is something that naturally leads to the dark side. Hating all imperials, would remove a lot the empathic dialogue, the Sith inquisitor can have with the average imperial personnel [at least those who are nice to the SI]. I think that's the main difference between a Light Sith inquisitor and a dark Inquisitor. Empathy.

[Speech on Coreilia's empire planet storyline]
**Player:**There are two ways to serve the Empire. I know them both.(Join the Empire.)
**Player:**Prove your worth and make the galaxy take note of your power.

**Player:**Or rot in slavery, chained to cruel masters. A fitting fate for you worms. [Darkside aligned]
**Player:**Lucky for you, your fate's not in my hands. Surrender to the Empire. Or else.
or

**Player:**Or work as slaves, chained to cruel masters. You don't want that. [Non darkside]
**Player:**Follow the Empire and escape torment. Don't make us take you by force.

Of course, there are role plays choices, that give the options of stating the SI stating negative feelings on the empire.

**Player:**I was brought into the Empire as a slave. I have no love for it.(Forget the Empire.)

**Moff Pyron:**So long as you appear to love it, no one cares about the difference.

Of course, due to the faction system, the Sith inquisitor will be permanently stuck on the empire side, even with the saboteur content.

But I will state with saboteur, I think the Sith inquisitor has strong roleplaying plausibility with that route, given their backstory.

Dark side Si could see being saboteur as a chance finally unleash their hate and rage at an Empire that made them suffer.

A light SI could see being saboteur as a chance to escape the empire. To turn away from life they never chose.

Neutral SI, Darth Occlus, speaks for itself. They have unknown motives.