You say that a lot has been left out, but leave out a lot yourselves.
This is fair. But I want to mention the "yourselves" bit. I do not claim to speak for other people, so that should probably be "yourself."
As to why I, specifically do not like him, there are a few factors. The linked image doesn't give a lot of context to the situation, but there was an incident where a teenager committed suicide, and the media heavily tried to make it appear to be a result of online bullying, when after an investigation, evidence was revealed that suggested that she sent the threatening messages to herself. Doesn't make the suicide any less tragic, though.
Around two months back, I believe, he was on this massive "de-anonymize the internet" kick. There was a lot of debate here, but his main point was that people should be held responsible for the things they say and do online, and so their personal information should be made available to the public. The image also shows an out-of-context chunk of a blog post he wrote on the subject. In it, he was trying to make his case, and he used the girl's suicide as an example of bullying leading to bad things. It was a factually-incorrect reference, and a lot of people, myself included, found it to be offensive fearmongering, to try and exploit a girl's suicide for pushing personal ideology.
Honestly, I definitely see why you are questioning the image; not only does it leave out a lot of context by default, but it Seels sort of propaganda-y. All those capital letters, red text - it feels so spiteful. I question anybody's motives when they make their approach with malice.
However, it's not just this one incident that bothers me about him. He has a habit of weighing in on issues, which isn't bad in itself, but often these issues are way out of his areas of expertise. I see a lot of interaction with him on Twitter, in particular, and recently he's been a lot less condescending and elitist. But a few months back, like every other day, I'd see him getting into arguments with friends and associates of mine, handwaving and ignoring people's concerns, and just generally acting like a twat. Some pretty malicious things, too.
I'm mean okay he seems to be anti-gamergate
This is a whole different can of worms.