You can when it's their job to know these things. It's what they do. If a giant spaceship can show up in NY, be all over the news, and they know less than anyone else, even while they already have a mission, then maybe they shouldn't call themselves SHIELD anymore. Mack was just standing there watching the TV. If he's got time to do that, he's got time to hit the "spy network" or whatever and find out WTF is going on- even if they can't do anything about it. It goes more to their skills to know, demonstrate that they have access to a bigger picture, even if they have to compartmentalize and let someone else handle it. I want a SHIELD that is fully aware and focuses on what they can do, not one that's just as clueless as everyone else and just reacting to what's in front of them.