What he did was OK. It broke no thread rules, and in fact followed precedent set by other people. Every leak has been talked about here. The thread has literally had leaked info in the title before.
I don't disagree that putting it in a spoiler tag is respectful, but I absolutely disagree that not spoilering it is in any way wrong or worthy of the reaction it got.
It may not be against the rules but as I said, it's a blatantly rude and disrespectful thing to do, especially in the manner Shiny did it (clearly clamouring for attention and nothing else). Some people did react rudely themselves but like I said, it's hard to sympathise when you basically asked for it. I've said many things here myself that I knew were controversial (though not for attention but more because I wanted to have a dialogue on the subject), and I don't expect sympathy for having overly emotional reactions and insults being thrown at me. I knew what I was getting into.
It's like when you say something to someone, like making a jab at something they did in the past that bothers them. They may react poorly and generally get really mad and shout things back at you, maybe even get physical depending on their temper and what exactly you said. You may not have broken any laws, nothing is written down that says you CAN'T say what you said, but you knew exactly what you were doing. You knew it was a sensitive subject. I'm not saying the person is right to shout back at you, ideally they would remain calm. But you knew what you were doing, you knew you were pushing buttons, and you signed up for such a reaction as soon as you pushed those buttons. You absolutely don't deserve sympathy in such a situation. You brought such a reaction upon yourself. If you were simply ignorant to the significance of what you took a jab at, then I could be more sympathetic towards you and would probably explicitly side with you. But if you knew what you were doing, I can't feel sympathy. Best I can do is diffuse the situation before anyone actually gets hurt any further, emotionally or physicaly, but if you say or do something disrespectful, don't be surprised if the response is disrespectful.
Obviously Shiny's situation isn't as extreme, but the principle is the same. He made a post that went out of its way to spoil people in a place where people have voiced that they would appreciate if the spoiler tag would be used when spoilers are involved in the discussion. Of course he was going to gather a negative reaction to that. The people who started swearing at him and what not shouldn't have done that, they should have kept their cool and remained respecful, but I would rather make sure Shiny realises the mistake he made and learns from it, than coddle him with biased sympathy and watch him continue pushing people's buttons. And my mind isn't going to change on that. All I can really do myself is advise him not do be doing that.
It may not be a rule or law, but it's one of those "unwritten rules" or life lessons that most people pick up on.
And for the record, I strongly disagree with blatant spoilers being put in the thread title, and think it actually should be against the rules, and I'm baffled it isn't. In this thread's case, it's a social thread. People aren't necessarily coming here for discussion on those spoilers, maybe they just want to socialise with some of the users they like hanging out with. People are going to open their alert box, see notifications for this thread, and before even realising there was a leak (or even realising there was a Direct on the way depending on how long since they'd been on social media), or before playing the game everyone is talking about and spoiling in the thread title, they've been spoiled and given no warning or chance to turn back.