In this case, we see that, because trademark does degrade if not defended, well, it has to be defended (no matter how silly it seems to do so). No doubt the Pork Board thought it was silly, but they really have little choice. If trademark was like copyright or a patent right, then they could have chosen to simply ignore this without much risk of losing their rights.
Because a few jokes about unicorn meat will degrade America's appreciation of pork. Certainly.
If enough people were to make jokes about "the other white meat" referring to various products, the pork board could theoretically lose the trademark altogether.
Foo *f = Other Foo();
They're so confusingly similar. ;-) But more seriously, I do agree with your point, if there's confusion (or the possibility), they would have to defend the trademark. I guess I just have a different bar for "confusing" than others.
Cats, the other white meat.
The NPB is completely fine with messing up chicken, but is concerned about the Unicorn Meat market infringing on pork products.
Now, those links and link text weren't on Thinkgeeks's site, but that fact only serves to make this look even more hastily done and less well-thought-out.
I'm pretty sure chicken might have a word or two to say on that topic...