Majority Opinion (a bitter 5-4 vote)

a.    Yes.  Justice Scalia, joined by four other Justices
(Rehnquist,Kennedy, Souter and Thomas), wrote the opinion for the Court. Scalia concluded that the law was impermissibly content-based, because “it
prohibits otherwise permitted speech solely on the basis of the
subjects the speech addresses.”
b. The Minnesota Supreme Court, in construing the ordinance, had
concluded that it was intended to apply only to “fighting words,” not
to bias speech that would not threaten an immediate breach of the
peace.  Scalia believed that he had no choice but to accept the
Minnesota court’s construction of the statute (but the problem
remained that the statute was impermissibly content-based).  Scalia,
because he accepted the Minnesota Supreme Court’s holding that the
statute was not overbroad, did not think that the statute was
overbroad (since the First Am. does not protect “fighting words” and
thus the statute cannot be overbroad).
c.  The Supreme Court has previously held in Chaplinsky and after
that the First Am. does not protect “fighting words.”  Nevertheless,
even though the government is regulating a supposedly “unprotected”
category (i.e., with fighting words), it may not do so in a
content-based manner.  Scalia gave two examples of what he considered
to be impermissibly content-based regulations of “unprotected”
categories: The government may proscribe libel, but it may not make
the further content discrimination of proscribing only libel critical
of the government. Similarly, a city council may not enact an
ordinance prohibiting only those legally obscene works that contain
criticism of the city government.
d.  But there is a caveat to the above rule.  Scalia acknowledged
that there is an exception to the rule that even unprotected
categories enjoy complete freedom from content-based regulation: when
“the basis for the content discrimination consists entirely of the
very reason the entire class of speech at issue is proscribable, no
significant danger of idea or viewpoint discrimination exists,” and
the content discrimination is allowed. Thus the state could choose to
prohibit only “the most lascivious displays” of sexual activity,
rather than all constitutionally-obscene materials; or, the federal
government can (as it does) criminalize only those threats of
violence that are directed against the President–each case, the
proscribed speech represents the most extreme instance of the reason
why the whole category is unprotected in the first place (e.g., it is
the “most obscene,” or it is the “most dangerously violent”).
d.    By Scalia’s standard, the St. Paul ordinance was clearly a
violation of  the First Am.  The ordinance was certainly content-based, because it applied only to fighting words that insult or provoke violence “on
the basis of race, color, creed, religion or gender,” but did not
cover, for example, political affiliation, union membership or
homosexuality.
e.   In fact, Scalia said, the ordinance was not only content-based
but “viewpoint based.” That is, where two opposing sides had a
confrontation concerning a matter of race or religion, one side could
use fighting words while the other could not. “One could hold up a
sign saying, for example, that all ‘anti-catholic bigots’ are
misbegotten; but not that all ‘papists’ are, for that would insult
and provoke violence ‘on the basis of religion.’ ” St. Paul has no
authority, Scalia asserted, “to license one side of a debate to fight
freestyle, while requiring the other to follow Marquis of Queensbury
Rules.”
f.  Proponents of the ordinance argued that even if it was
content-based, it could survive the strict scrutiny given to
content-based regulations because it was necessary to serve a
compelling state interest. Scalia conceded that the state had a
compelling interest in safeguarding the rights of
traditionally-disfavored groups, including their right to live in
peace where they wish. But he argued that the ordinance was not
“necessary” to achieve this state interest, because there were
“adequate content-neutral alternatives.” In particular, St. Paul
could enact an ordinance prohibiting all fighting words, not merely
fighting words motivated by racial, religious or other
specifically-enumerated biases.