The original is relevant because 1) it is valentine's day and 2) most people here appreciate a good math formula.
On it's own the original post was perhaps not too original, but it spurred some interesting discussion, like where the heart shape originated.
The penis graph on the other hand, only comes of as childish. Sure, it would have been really funny when I was 15. And to be sure, there are plenty of clever penis jokes out there ("The hammer is my penis" comes to mind), but this is not one of them.
I can see your reasons, but to play devil's advocate (because it's more fun):
1) via Wikipedia, the heart shape itself is likely based off the shape of the silphium seed, which was used as a contraceptive, or of course various naughty bits of anatomy. And condom sales spike around V-day. Relevancy #1: check.
2) It's an equation. And it even contains pi raised to the pith power. Relevancy #2: check.
> The algorithms that Taubin developed worked well even in the vicinity of cusps and other singularities. "I discovered the equation of the heart while trying to construct surfaces with complex singularities," Taubin says.