^ The only exception I take on that is when your life is in danger. If a hostile alien life form wants to kill you, you have to defend yourself regardless of whether you are an intruder. True, if there's no means to communicate that there's no hostile intention, you still don't want to kill them outright, hoping you might be able to neutralize the situation... but they killed several crew members. I think vaporizing a shield or weapon of theirs would scare the living daylights out of them. They are intelligent, yet they are primitive with a very low tech existence. The tech possessed by the landing party would be magic in their eyes, something to fear if it proved powerful enough to make something of theirs disappear in a fire ball flash.
Some of what I don't like about the episode I chalk up to a limited budget. This was the first time they were using the shuttlecraft, an enormously expensive prop. I do wonder if this was weighed into the cost of the episode or amortized across the entire life of the series as a "long term" prop. But in any case, we see very little in the way of special effects where the phasers are concerned. Just a few beams here and there, no exposure of the result (phaser burns or vaporized objects). They may not have had enough SFX budget to show, thus they conveniently left this out. So instead, there's this thick mist where you can't see your enemy, then suddenly they emerge and launch a spear into your gut before you can fire your phaser at them.