It would certainly be undeniable proof of Poes law.
It kind of reminds me of another Far-Right lawyer, good ol' Jack Thompson, when he tried to announce he was going to prevent the release of Halo 3 the day after it had been released. That was nothing whatsoever to do with the content of Halo 3, and everything to do with the fact that the game was getting far more attention than he was, it didn't take a genius to work that one out.
Phelps works along much the same line, he's realised that the more offensive he is, the more attention he gets, and then he scampers off and hides behind Freedom of Speech when he gets caught, he's actually found a way to turn one of your main strengths into a weakness.
If he simply stated his opinion, it would be different, but to actually go to those funerals and attempt to incite anger is, to my mind, going beyond the freedom of having an opinion and into attempting to create anger and strife through physical activity.