I think that publicising the fact that they're an ABORTION organization, and that they're proud of killing (any baby, any size, for any reason!) is a terrific idea. If enough people (i.e., VOTERS) notice, maybe the government will stop giving PP our tax money and pretending it's for "women's health"!
I'm sure this will happen right after the NAACP loses its tax exempt status.
Another approach might be to bring up PP's past association with the eugenics movement. On the back of their t-shirt, you could add, "...and helped improve the human race!"