Same happens in italian where English words are used to sound fancy and hide behind technicisms. Sometimes it gets funny because you end up with words like "devoluzione" coming from english "devolution" (which in turn comes from latin) replacing the italian "decentramento".

"obese" doesn't sound less rude per-se because it's latinate, but because, being latinate, it became a technical term and thus can be used to describe something with more distance, and apparent objectivity.