4chan memes, goatse, tubgirl etc. seem actually valueless. I personally see almost no value in theology once philosophy started talking about the same things without reference to God. Great swathes of the critical humanities are circle jerks of interest only to people in the same very small niche, which nobody outside academia cares about.
Your time can be better spent than learning about these things. They might be interesting but they're no more worthwhile than Cougar Town or How I Met Your Mother
The point is not that you must strive to be an expert on everything. You don't have to know everything (or even very much) about theology or How I Met Your Mother, but you should have heard of them and perhaps even have a vauge notion of their central themes. In this day and age you can gain a superficial knowledge of just about anything in less than 10 minutes on wikipedia and with the ubiquity of the internet knowledges can easily be JITed in as and when you need it.
Hell it's even perfectly OK as such to be completely ignorant of a field. Just leave when a conversation on that topic strikes up or sit quietly in the corner and try to learn something. I'm just perplexed by people who feel the need proudly proclaim "I know nothing about TV/books/computers/sports/music etc." as if it was some sort of achievement to be proud of.
I think your examples, while possibly somewhat contrived, fall quite flat.
I personally would be proud of the fact that I completely ignored anything related to "How I Met Your Mother" to delve deeper into the field of mathemetics, for example. I don't know why ignorance on a subject is so unforgiveable in your opinion.
That said, I quite enjoy HIMYM, but I certainly wouldn't fault anyone else for not having seen it.
It's not the ignorance in and of itself. Nobody is judging patio11 based on his (lack of) knowledge of metal singers. It's (1) the proud announcement of ignorance and (2) posting it in a message as if it contributes to the discussion. If all you can add to a conversation is "Is this something I'd have to own a TV to know about?", do us all a favor and don't click the reply button. There's no requirement that you post in every thread, and an article on A/B testing will come down the pike in just a few minutes.
Your time can be better spent than learning about these things. They might be interesting but they're no more worthwhile than Cougar Town or How I Met Your Mother