It can be very rude.
My two daughters were in a play recently with six performances. Parents were welcomed to take lots of photos during the two dress rehearsals (I took and posted hundreds), but once opening night came I was not going to film or take photos. That's just rude in a theater.
Sure enough, one of the actor's mothers pulled out the ipad and filmed it, which not only blocked the view of several people, but cast a light in the faces of a dozen audience members. I couldn't believe how rude it was.
It has nothing, however, to do with Apple or fans of Apple. I love my Apple products and use them daily, but I'm not ever going to pull out an electronic device in a dark theater, making it a problem for others.
If someone wants to take pics of their kids at the park, however, that's fine. It's none of my business what they do. For it to bother me would be my problem. Why should I care?
It's only a problem if it inconveniences someone else.