T'Pol Asks Captain Archer to Leave Her Behind.

"I can't try to save humanity without holding onto what makes me human."
- Captain Archer

They find this material to line the hull of their ship with that will protect them from potentially deadly anomalies. But, as it turns out, the material is somewhat toxic to Vulcans since it makes them unable to control their emotions.

It's interesting because, one or two episodes earlier he decides to torture an alien who invaded his ship but, ultimately, decides not to kill his prisoner. The writers didn't directly point it out but, you can kind of see in that episode that he has already made his choice to be a humane captain.

I feel like this is especially poignant in the current social climate we find ourselves in. Things here in the US seem like they've calmed down a little but, it's important to remind everyone just how easy it is to walk down the path towards extremism. When you find yourself assigning attributes to an entire demographic of fellow humans based on something you've seen two people doing, then you're already on your way.