The short version is, try not to annoy people or get so annoyed that you take leave of your senses and make a huge fool of yourself all over the internet. The trick is to understand which way the wind is blowing and take a pragmatic position in order to maximise success.
For example, when Matthew Inman discovered that Funnyjunk was hosting images he had created without even linking to his website, The Oatmeal, he had a rant about it and let it go, realising that it's impossible to police a user-generated content site, and pointless trying to persuade people to stop uploading their favourite Inman images. Realising that this will almost certainly happen if you have a good product, the trick is to harness all that goodwill and excitement by making a deal with the offending site and asking them to carry ads or otherwise link back to your site, and to encourage users to credit creators. Or you could get Charles Carreon to sue them for you. Good luck with that.
Other people's articles
Judith Griggs, editor of Cooks Source magazine, lifted an article written by Monica Gaudio and posted it without notifying Monica or asking for permission. When Monica found out about it and complained, Judith wrote a high-handed and patronizing response that ignited an internet firestorm, according to Dylan Stableford in an article on thewrap.com.
Posting someone's work in full, even if you credit them, can get you into a world of trouble IF you do so without their permission. I use other people's content all the time in my own blog posts, particularly when reporting internet news. The difference is, I only use as much as is absolutely necessary, and when I use a lot, it's to advertise the other person's work, not to merely take it for myself. I generally just use a snippet and link to the source.
Anyway, Judith decided to simply lift the whole article, make some editorial changes, then sniff haughtily at Monica when she complained. Bad, bad bad idea. She should have apologised and made it up with her. She didn't, and lost her job over it. And her reputation.
It'll happen. Get over it and move along. Or you can engage with the people who are saying these things with a view to sorting things out. The last thing you should do is try to shut it down with legal threats. That will massively backfire. Sometimes criticism is deserved. If you demonstrate that you are reasonable and willing to work towards a resolution with a disgruntled party, you can end up gaining more business. I've never had anyone call me out online for bad service and hopefully they never will. That's because I work to resolve complaints before the matter goes public. Mind you, my policy of letting the client pay me in milestones means that they don't pay for work they're not happy with. Result: there's little to complain about.
So you've made a huge fool of yourself
Sometimes people do that. The thing to do is keep your head down and wait for it to blow over. It will. The internet will move on unless you've done something particularly memorable. Don't be defensive or otherwise try to control what's going on. You can't. Momentum will carry the crowd however good a case you make for yourself. Wait for the heat to die down, then carry on. And for goodness' sake, learn from your mistakes.
I hope that helps. I often write about this stuff so keep an eye on this blog. Enjoy the comic! As ever, it's free to share as long as you cite and link me when you do, and don't try to pass it off as your own work.