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.
"The first stage of grief is learning to pronounce the disease #joke #black humour #funny #comedy"
You'd look like a colossal ass if you did that.