Listerine burns your tongue because of the alcohol in it. "Alcohol burn". The more it burns, means that there are a lot of germs on your tongue and mouth that the alcohol is killing.
Feel a little tingle burn? Thats the alcohol at work killing the germs. If you're sensative enough you can feel it. The more you use it and the more often you brush your teeth etc, you may notice the pain going down. I brush my tongue with the tooth brush at least one of my brushings. Brushing your teeth lessens those germs to be killed by the listerine.
I hope this helped ^_^