I don't know them!
I heard that he said something derogatory about people being pissed off, something like 'it's just tits and dragons'.
I think this is sad. Because the people who don't appreciate getting things spoiled aren't the same tribe as the typical crew of internet users who lose their minds over every little thing. Not wanting things you may enjoy ruined for you is a much older thing then the internet.
Mr. McShane is on the wrong side of this one. Not all of us can watch everything the moment it comes out, and so we have to fight to avoid spoilers, and we've all had some douche-nozzle ruin something we were enjoying with a careless Facebook post. We don't try to avoid these spoilers because we assign too much importance to 'tits and dragons', we just want to be able to enjoy the entertainment we choose. We want to lose ourselves in other worlds and care about characters. That's what storytelling is for, and it pays his salary.
On a more personal note, epic fantasy stories are a little more than 'tits and dragons' (though don't get me wrong, that's a funny-ass thing to say). This feels a little like genre diminishment, which pisses me off a little. The fact that Game of Thrones is as popular as it is says a lot about the mainstream acceptance of the thing I love the most, and people saying it's 'only' anything is an antiquated notion. We run the world, now. Comics, sci-fi, fantasy: they aren't beneath any longer. They aren't just 'men in tights' or 'space battles' or 'tits and dragons.' They are mainstream entertainment and their metaphors serve to expose messages of humanity to those who can't see them without the genre staples. They are valid forms of entertainment and art.
Comes down to the fact that he's entitled to his opinion, and as I said, I think it's just misguided. For him to group a spoiler from his own mouth with the over-aggrandisement of everything that ever touches the internet and its legion of trolls and asshats is understandable. It's just flawed. My friends and I hate getting things spoiled because we care. We also think that people freak the fuck out too much. In almost every other situation where a celebrity has gotten chewed up on the internet for little reason, I've been on the side of the celebrity. But this?
Again, I don't know what the spoiler was or how big it was, but after reading five books and watching as many seasons of this show, I'd probably be pissed off too if I had something important ruined. And I would have every right without getting grouped in with soapboxing weirdos who have nothing better to do with their time.
Short Answer: I really like Ian McShane as an actor. That won't stop. I hope he's good on Game of Thrones and I hope this nonsense doesn't alter my enjoyment of the forthcoming season.