I engage with em. Toss memes around and belittle them. My customers defend me. I also ask for order numbers and I see how we handled the sale and customer service. If we fscked up, I own up and fix it publicly in the comments (refunds, or resends) Most of the time they didn't buy from us, or purchased from a shitty competitor. If they're crazy, I post email exchanges and proof that we handled it appropriately. People really like this, and I get lots of customers saying they buy because we're honest, funny and fair.