That is how twitter jokes look. It is part and parcel of the medium. Better to have the joke look like a twitter joke and get read by an audience, than to make it pure and read by nobody. Really, the hashtags are no more out of place than a smiley face on an email.
I don't use Twitter, but based on what I see on Instagram, I agree with the parent that those people look like asses. It comes off as whoring for followers, and a bit desperate.
I think it's different, however, if there are a few hashtags at the end which in themselves are jokes or metajokes and that add to the cleverness of the post, in the same way that XKCD alt-text does. A string of simple categories (#joke #jokes #funny #comedy) is just annoying.
And yet, many popular users do exactly that. I'm a huge proponent of keeping metadata, which is what hashtags are, out of the data. It sucks but, making your message "discoverable" pollutes your message.