We haven't seen it being Imperial protocol to conduct such wanton random acts. Lord Vader seems to have issued instructions to board and capture the ship. And the troopers seem to even fire warning shots if anything. I actually like watching ANH after ROTS, because it makes it feel like, "Who are the good guys here?", as we watch Imperial (formerly called Republic) troopers storm and board a vessel. Notice how also the troopers are to take prisoners alive. It is my understanding that at least on Vader's personal Destroyer etc that these were the highly professional elite (whether they be clone or otherwise) troopers. And they obey orders without question. They aren't rogues or succumbing to evil acts. And the Imperial Commanders would only issue instructions consistent with their objective. To find the stolen plans by the Rebel (scum) spies. It wasn't any part of the mission to take out uninvolved persons. As for the Jawas, I do believe Obi Wan when he says only Imperial Stormtroopers are so precise. Though one wonders how he knows haha. Or whether he is attempting to seed doubt into a young Luke, who was just the previous night, once again reiterating his long term desire to go and join the Imperial Academy to train as a pilot. The Jawas were criminals though. Even Uncle Owen had accused them of trying to "push on him" junk. That is was stolen might even suggest during the questioning, the Imperials discovered the illegal racket and attempted to arrest them, to hand them over to the local Governor's authorities/local Stormtroopers. But the Jawas may have resisted, forcing the Troopers to defend themselves. I don't think everyone in the Empire is evil. Only the likes of Tarkin and that other Moff who got choked by Vader appeared to be quite genuinely mad. But not all forces would have been under their command. It's just that the Empire literally gains nothing from attacking the Homestead. We are meant to assume it was the Empire. But if anything it serves only to turn Luke, an Imperial citizen, against them. I agree. You do realise that Obi Wan was once a Jedi? Burning a Homestead, it's just not in his character... To be honest I do find it hard to believe Obi Wan Kenobi would do it. But likewise, I don't feel that the Imperials attacked the Homestead either. Unless there was proof that the Lars had openly colluded with the Rebellion, what reason or gain would the Empire have to do this? Luke himself was trying to join the Academy (Imperial Academy) every year it seems.