Was someone just trying to be funny by being ironic?
Sesquipedalian means having many syllables, and you'll probably know what phobia means. Thus, "sesquipedaliophobia" is an irrational fear of words with many syllables. The prefixes "hippopoto-" and "monstro-", as you might guess, are not there to add anything in terms of meaning, in fact they are rather nonsensical. Their only purpose is to make the word longer, in a witty and cruel, sarcastic twist.
So I guess the answer to your question is yes, you can say that someone was trying to be funny.