No, I don't think it's meant to be derogatory, simply shorter to type than the full name which invariably contain typos. The ISrael bashers' use of the word "zionists" ( with out a capital Z) is however used in a derogatory way - as you may have noticed, and is used in this way in most anti-Israel propaganda. Those who use it in this wy are of course ignorant as to its real meaning and adopt it as it's used by those wishing to insult Israelis/Jews.
Military police vehicle attacked by rioters overnight in ultra-Orthodox area of Ashdod (Haaretz)
from the article: Arab tradition makes a comeback - on TV