Okay, so we've pretty well covered how not to talk to and about people you disagree with, right? It can be summed up pretty easily by asking yourself the following question: Does this thing I'm writing/saying/drawing/etc. actually address the substance of what the person I'm talking about is saying/writing/drawing/etc.? Or does it attack irrelevancies? Because focusing on what someone says and addressing that, rather than changing the subject to their looks, their credentials, or anything else isn't just polite-- it's good arguing. It's Lesson #1 on Good Arguing, perhaps Remedial Good Arguing.
Another way to attack irrelevancies rather than the substance of your opponent's argument is to attack arguments your opponent never made. This is typically called strawmanning, although if you go the lengths of flat-out quoting them saying something they never actually said, I think that's called plain ol' lying.
The quote is suspicious to me right off the bat for two reasons: 1) I know that Richard Dawkins considers himself a "cultural Christian," meaning that he acknowledges the extent to which Christianity has shaped the culture in which Westerners live, and sees no conflict in appreciating those elements of culture as an atheist-- a standpoint which I wholly agree with, although I don't really like the term "cultural Christian." It's too confusing without the explanation. 2) I have gathered, though I couldn't tell you from where, the understanding that Dawkins has close to zero knowledge of and interest in video games. I'd be surprised if he knows what "RPG" means.
However, that's not going to be obvious to everybody. All that a lot of people know about Dawkins, people who despise him and people who love him, is that he's an atheist who opposes religion. And there's no shortage of atheists who would most likely agree with the first part of the quote (or rather "quote," I suppose-- putting scare quotes around the word "quote" is so meta), if significantly fewer who would agree with the second part.
I don't know whether John the Secular actually created the meme he tweeted, or just found it and commented on it. If the latter, then he's just guilty of being credulous. But that's an important part of not attacking irrelevancies-- don't be credulous. Don't just assume that a statement you see attributed to someone you want to attack is authentic, especially if it seems too "good" to be true. As in, laughably easy to discredit and mock.
It's possible the meme was made as satire, but if it's intended to be satire then it fails-- no clever point is made, and gosh, if you wanted to satirize Richard Dawkins it would be so easy to do better. There's ample material out there-- no need to create new, false statements to attribute to him.
If it's an attempt to satirize Dawkins' detractors....no. That's not how you do that, either. If they believe the quote, then again-- they're just guilty of accidentally buying a lie. But if you created it, or passed it along, you're guilty of selling it to them.
Making good arguments requires skepticism. And skepticism needs people who can make good arguments.