The first thing to know is that facts do not matter. This is a fact of the Internet. This fact doesn't matter. Everything you know or think you know is automatically wrong on the Internet. Do you have statistics, figures, charts, and graphs backing up your position? Is your position common sense and the only logical choice? Too bad. Facts are all fake on the Internet. Prepare for constant intellectual outrage and absolutely zero intelligence while navigating the murky swamp of social media and comment sections.
The next thing you need to know is that everyone on the Internet is way important. They all have very prestigious and mysterious careers and positions that put them in the know. Don't question them because they know things you're not allowed to know. Pay no attention that they are spilling this secret knowledge that they shouldn't be telling you. They may also know various people with various diseases. They themselves may be a human petri dish full of disease. This inoculates them to any logical argument. Unfortunately, it doesn't inoculate them against their many diseases.
Keep in mind, though, that you are not important. You are, regardless of reality, a parents' basement dwelling pedophile. You have no education and no job. You're probably fat too. Being fat on the Internet automatically invalidates any informed argument you may have. Don't be surprised to learn you're a homosexual either. Take your gay, overweight self back to your mom's basement and don't question the doctor-scientist spy with AIDS cancer.
Another surprising encounter you may have is that any logical argument can be boiled down to 140 characters or less. No matter how complicated or nuanced the subject. Any good argument is directly related to if you can tweet it. Leftists and atheists will provide you with all the Twitter wisdom you can handle. If you think you can provide them with a thoughtful answer in response; don't. If you write it out in its entirety, they will inform you that it's too long. If you tweet it, they will let you know that such matters can't be discussed in any meaningful way over Twitter. They're all super awesome philosophy astronauts and best friends with Richard Dawkins, so they can use Twitter to mock their interiors. You can't because? That's right, you're a fat, gay, basement dweller.
Fought a civil war to end slavery, brought equality to everyone, accepts the world's unwanted masses, protects personal liberty of all kinds, major technological advances, unprecedented reduction in poverty rates, and an amazing quality of life are all things that Western Civilization has been used to bring into the world. It doesn't matter. Western Civilization is the greatest evil perpetrated against the world since time began. Did you know they used to commit some of the sins that the rest of the world still commits? Nevermind that slavery is still a thing in the Eastern world. The West used to own slaves! I can't do this segment of the post. The arguments that the West is evil because of their past, in light of the fact that many nations still carry out such atrocities, is so ridiculous it doesn't deserve repeating.
There you have it! You now have a starter's manual for you to use while surfing the Internet. When you find yourself in the middle of a comments war because you had the audacity to agree you may find that this list is unfortunately true. What's that? Oh, yeah, I said agree on purpose. This is the Internet and you never know what will set someone off. You may even find yourself in an argument and then realize that they accidentally started an argument with you when they actually meant to argue with someone other than you. This will start another argument.
The advice you may find the most useful is: don't be sensitive and don't take it personally. Believe it or not there are some people out there that handle every time on the Internet like a teen boy handles his first beer. We also have people who handle it like every girl who ever takes a sip of alcohol. That's why we have so many naked selfies floating around in cyberspace. That's only a half joke.
Well, welcome to the 21st century, enjoy the hell your descendants have created, and don't be frightened by the 12 year old who claims to be a super awesome hacker who will find you and beat you up. That only happens rarely. They're most likely only going to SWAT you.