This article in the New York Times leaves out one significant reason that many Arab citizens of Israel oppose voluntary national service: Arab women in Israel typically are either discouraged or forbidden from working outside the home, very few are employed for wages, and many rarely leave their villages. Of the small percentage of Arabs who do national service, the great majority are women who are seeking opportunities otherwise denied to them by improving their Hebrew, gaining work experience, etc. This is a threat to traditional (let’s say it forthrightly, backwards) mores in Arab communities in Israel, and explains at least some of the growing hostility toward national service among young Arab men.
(For both libertarian and pragmatic reasons, I’d prefer if Israel would switch to the extent national security allows to voluntary national service for the entire population, including army service. Israel could start by ending the draft for women; women serve primarily in clerical positions in the military, which could easily be filled by civil servants.)