Superstition is Rife among developers
There is a class of persons (happily not quite so numerous as
formerly) who think it enough if a person assents undoubtingly to what
they think true, though he has no knowledge whatever of the grounds of
the opinion, and could not make a tenable defense of it against the
most superficial objections. Such persons, if they can once get their
creed taught from authority, naturally think that no good, and some
harm, comes of its being allowed to be questioned. Where their
influence prevails, they make it nearly impossible for the received
opinion to be rejected wisely and considerately, though it may still be
rejected rashly and ignorantly; for to shut out discussion entirely is
seldom possible, and when it once gets in, beliefs not grounded on
conviction are apt to give way before the slightest semblance of an
argument. Waving, however, this possibility—assuming that the true
opinion abides in the mind, but abides as a prejudice, a belief
independent of, and proof against, argument—this is not the way in
which truth ought to be held by a rational being. This is not knowing
the truth. Truth, thus held, is but one superstition the more,
accidentally clinging to the words which enunciate a truth.
Have you ever heard Perl and PHP fans get stuck into each other, or Java vs C++, or Vim vs Emacs (there can be only one). It’s crazy! Most of the noise is created by people who have no real understanding of the technology they are arguing against and some of them don’t even understand the tech they are arguing for. Wikipedia has an entry on Editor Wars.
Basically Mr Mill is stating that if you are arguing against something with little real understanding about what that something is then your just another superstitious idiot.