This is just plain rude... but it's not as bad as the dumb fucks who go up front at a show because they WORSHIP the headlining band, and then turn their backs, or even boo, the openers, and/or yell the headliners' name through their set. These fucks seriously need to be beaten to a pulp.
I saw this happen at Fates Warning/Savatage, and I've heard about it at countless shows (such as Event/Symphony X) where the support band and headliner play very different styles of music. If you can't at least be POLITE, then don't stand up front. You couldn't possibly be any more of a dick, even if you stayed away during the support acts and then pushed and shoved your way to the front for the headliner.
There's a lot of behavior during shows that I find annoying... I absolutely ABHOR this shit.