As far as Apple forcing you to install updates, that is only in regards to security updates stored in XProtect. The setting is tucked away in System Preferences > Security & Privacy > Advanced > Automatically update safe downloads list. This is the reason why you can't install old versions of Flash or Java, even if you haven't run software updates in a while.
As for the OP, I agree that this message is very annoying and needs to have a way of disabling it. The really annoying thing is that the only way to get rid of it WITHOUT running updates is to click details and then quit the App Store. That gets so tiresome. I just want OS X to download the updates in the background, maybe even notify me that they were downloaded, but then GO AWAY when they are done! It's not the notification that annoys me but the process it takes to get rid of it. Just have it fade away after 5 seconds or put and "X" in the window so I can close it. I shouldn't be forced to go to the App Store.