Although I've never done it with a light (not sure I own one that would) I've killed spiders. Usually (inadvertantly) with poison while killing other bugs. Sometimes grabbed them with toilet paper and flushed. I try to let them live. Haven't hugged a tree in a long time, and never on purpose!
After seeing what Brown Recluse bites are like, I didn't feel quite as bad about it, though I agree most are beneficial. And out in the country where my friends live, Black Widows abound. I tumped a canoe with other people in it at their place. I was pushing off a tree branch that was leaning in to the water. Hundreds of baby Black Widows (at least I thought that's what they were) began to jump on my hand. I, of course, being the calm collected dude I am, panicked and brushed them off furiously, tilting the canoe in one direction. I then over compensated a swing back in the other, and ta da, instant swim session. We still laugh about that.