I would advise to slow down aswell. Don't get bullied by anyone into speeding up just because they are 2 inches from your bumper. If they continue to tailgate even after you've slowed down you'll know that if there was to be a collision, they would hit you at a slower speed. Generally, if I am being tailgated and I slow down, the car behind tends to overtake anyway. Which is fine by me - I'm happy to let them take their dangerous driving somewhere else. Also if you are getting blinded by lights in your mirror at night you could always flick the rear view mirror to the anti-dazzle position?