LPJ appears guilty of the same crime I often find I've committed - not being funny.
I can see where he thought this (including the reference to the 'webcomics killing newspapers') was hilarious. Because it's stupid. You don't - can't - kill WotC by playing Pathfinder. The two have little-to-nothing to do with each other; the shirt is an ironic slap-in-the-face to those who think they do.
...aaaaaaaaaaaaand I'm in no way surprised nobody got it. Heck, I didn't get it, until someone pointed out the exactly-the-same-joke Webcomics shirt.
So, yeah. LPJ isn't funny. IMHO, he's a little bit too clever to be funny (and trying to hard); like I used to, he makes jokes that require three lateral leaps in logic and one obscure reference; if you get all of them, they're hilarious; if you don't, everyone looks at you like you're crazy and the conversation continues without you, and your friends sit around later and talk about what a socially inept baboon you are.
The answer to this is for him to continue to be unfunny*, until he either finds people who do find him funny, and then hang out with them, or until he learns what most people find funny, and does that, instead.
It's not dissimilar, really, to some people laughing during Spinal Tap, some people laughing along with Sasha Barat Cohen, some people enjoying the very few jokes hidden in and about Wikipedia, and some people laughing during America's Funniest Home Videos. To the right group of people, the shirt is hilarious, and inoffensive. To the wrong group of people, it's nothing but videos of people getting hit in the groin.
Wait, I might have mixed that metaphor...
* - Yes, this could bode poorly for his business.