Report them to their web host and the ad networks they use. Don't troll them with different content just go for the kill - some accounts like AdSense carry lifetime bans.
Luckily they are stripping out the ad tags before displaying by site so it shouldn't affect Ad Sense.
Don't just block the /24 ("Class C" IP block), block the /16 ("Class B" IP block) the IP resides in. You'll reduce your audience in India, but they'll have to switch webhosts to continue leaching his/her site.