I think it's pretty obvious, if you know about the "god hates fags" thing, that that is indeed a parody. Especially since one of the signs is "God hates mopeds".
And I'm pretty sure not everybody has heard of this character, so it's not their fault the media hasn't fed mr. Phelps' ego by making him even more famous.
And no, I also doubt that phelps would picket a moped ride, if nothing else because protesters on foot can't follow a moped rally at 30 MPH.
Bikers picket fred phelps, though.