Aggressive touts are a fact of life for Western travelers in hyper-capitalist China, and the more well-trafficked the area, the more numerous said touts. Guangxi province is known for the tenacity of its touts—mostly older, tribal women with silver teeth (as is the local custom). To these wandering merchants, a Western traveler is a coin purse with legs.
It's not uncommon for half a dozen of these women to surround you at any given site, shouting "water" and "postcard." They'll follow you around until you buy something from each of them.
It's hard for travelers to maintain equilibrium when confronted with a gaggle of old women who seem doggedly intent on turning a hiking trip around, say, the Longsheng Rice Terraces into a no-win trinket-buying binge. Polite "no, thank you's" can soon become expletive-laden tirades, inevitably leading to remorse for cursing a poverty-stricken old woman.
What's worse, cursing accomplishes nothing. No sooner will the last bitter word leave your lips than Granny will thrust a pack of commemorative postcards at you and shout "10 yuan!"
Our advice is to consider the purchasing of minor souvenirs or unwanted sodas as part of the experience, keep a few yuan handy for just that, and to deal with it smilingly. Failing that, you can always run. But remember, these old women know all the shortcuts, and you'll tire out and need to buy a beverage anyway. And maybe some postcards as well.