The view is vague. Forgetting the source also makes it hard to credit this as totally true.
Assuming you didn't just make this up though; where I'm at, people don't game out in public. At best, you have somebody with their PSP out. You don't see anybody with a DS out. I have yet to even see a 3DS in person. Fact is, people are embarrassed by the product. Yeah, it may not apply to you, but people have a tendency to apply video games to a negative view, and even more so with anybody that is familiar with the content of Nintendo.
There are some people that are barely even willing to mention that they play video games, as it's considered just oh so nerdy and unacceptable in most society (or at least mine). A lot of places don't seem to care as much, but I'm in a community where you just don't see it. Nobody seems to care when it comes to Sony products though. Maybe because Sony is directed towards an older audience, so people don't care as much. Whatever, doesn't really matter.
For the person mentioning the touch pad on the NGP to counter against the motion gaming bit; touch pads aren't motion gaming. The Nintendo Wii, Playstation Move, and Kinect are motion gaming devices, as they register your movement for the movements of characters or objects within the actual game. With touch pads, it doesn't register movement, only the fact that it's being touched. You also have to remember that Sony hasn't based a system around motion gaming, though they did hop on the motion gaming bandwagon. They lost room to mock motion gaming at that point.