When you hand out po-faced advice in a mature as fashion as you can manage, without realizing you just don't get the joke.
I've been alive for a while to understand what a 'useless lesbian' is and how it's used, both online and in-real life within the communities. I'll admit though I didn't think your comment was a joke at first, I thought it was an acual jab at lesbians due to the wording.