Language is a democracy. When people say thing like "My head literally exploded", they are voting for "literally" to be a meaningless intensifier. When I make fun of them, I'm voting for it to have the meaning, "This actually happened".
Think about which way you want the language to be, and then use your vote.
Democracy implies you both have equal votes and there is an outcome that can become the norm. They are using the word 'literally' in a way that imbues additional meaning (or arguably makes a new word) without seeking permission from society or community. You are using (mild, well-meant) social coercion to try to suppress that usage. I'd say it's more anarchy than democracy.
I don't think the intensifier is meaningless. It is meaningful because otherwise people wouldn't use it. It might be jarring to you, or the meaning not obvious, but an intensifier is by definition meaningful: it intensifies, after all :)
Exactly. The post I argued against didn't provide any information about base rates, so it was not the kind of argument from popularity that you're describing. A lot of people write English. You can always find someone who screws it up in some way or another. Pointing out these screwups is not an argument that the screwup consists of a consensus language change.
Think about which way you want the language to be, and then use your vote.