Just because no-one is literally drawing a moral equivalence between her and Hitler doesn't mean it's not a shitty thing to say, or that you're not a dick for saying it.

I think you would be a dick to send that joke to /u/ekjp, and it's a bit crass for a dinner party, but it's well within bounds on a pseudonymous forum called "Jokes".

Now, I think one could make the argument that /r/Jokes should be more heavily moderated because it's a default sub, and should cater to a more vanilla, easily offended audience.