Whenever someone says "DON'T DO X!" in a movie, where X is go into an abandoned building, open a mystical old book, or walk into a creepy mist, you know someone just has to do it. Of course, we have the advantage of knowing that The Mist is bad from the get go, but come on people .. it's a freaky mist from out of nowhere. What makes them think a bundle of twine is going to keep Andre Braugher safe?
You've got wailing sirens going off, people screaming left and right that there's something in the mist, and this guy thinks he can make it to his car. Pure genius.
All we can say is, you're going to need one hell of a big can of Raid to deal with these things. Plus, if they're anything like our houseflies and their lifespan is about 20 days long, what happens in three weeks when you're wading around in insect corpses three feet deep? Hopefully that dimensional rift brought over some Venus Flytraps as well.