I would simply ignore them. The fact that they are attacking you shows they are weak, insecure, have issues of their own, wanting to desperately prove that their purchase was better than yours. I already had a personal dislike of Apple and the iPhone beforehand, but its been magnified working as tech support at VZW. As said before, sweeping generalizations are typically inaccurate.
But so far in my experience, the iPhone customers I help tend to be more arrogant, rude, rushed, impatient than their Android counterparts. They'll blame me if iTunes botches the firmware on their precious iPhone during a failed update. They'll blame me if they have issues with DRM on iTunes. One was a customer with us since 1993 and he wanted to leave simply because ATT had a better price on the iPhone (mind you, it was $49 for a 3GS model). I can't believe someone would leave after 18 years with a company because of this, but this is the "god" phone we are talking about here, it does crazy things to people!