Walter Palmer woke up Wednesday as the world's most despised dentist, facing a PR challenge a lot bigger and scarier than any lion. The big-game hunter is at the center of a worldwide uproar over the death of Cecil, a famous lion in Zimbabwe. Palmer shot the lion in what game officials say was an illegal hunt and temporarily shuttered his Bloomington practice as police prepared for protests. The practice's Yelp.com page (which now has a one-star rating) racked up over 2,000 reviews by Tuesday afternoon,…