Thespian*: Nothing at all, but to use that reply when another user is trying to elaborate his stance, when one isn't even involved in the discussion, it's pretty dismissive, don't you think so?
I think this is an issue of language, you can't judge what you hear on how you would speak (or literal interpretations of humour, which would really screw with you if you came to the UK) you have to accept that cultural differences between countries (and even differences in the same countries) can have a big impact on what is said and what that means.
There was nothing wrong with what they said, it was just humour and in no way dismissive (id suggest it was friendly and meant to make the situation better/lighter in fact).
Maybe it is not the type of humour you get and/or use but that does not change its actual meaning or make it wrong.
Thespian*: I know the meme, but (from the very page you linked): "the phrase has been colloquially used to advise someone against over-drinking
or scold him or her for losing self-control".
"colloquially" changes across the world, and across same countries that is why colloquialisms are not formal usage. It even becomes more complicated because although technically I have heard it in this meaning, it is dependant on context and how it is said. Like many things in the English language a word or phrase can mean completely different things depending on how and where it is said.
In this case I can see no context where it could possibly mean it in a bad way at all.