Democracies and double standards

Timothy Garton Ash in the Grauniad raises the question of how multicultural societies have to accommodate difference without giving up freedom. His approach makes a lot of sense:

If someone says "the Nazis didn't kill so many Jews and had no plan for
their systematic extermination", he is a distorter of history who deserves to be
intellectually refuted and morally condemned, but not imprisoned. If, however,
someone says "kill the Jews", or "kill the Muslims", or "kill the Americans", or
"kill the animal experimenters", and points to particular groups of Jews,
Muslims, Americans or animal experimenters, they should be met with the full
rigour of the law. That's why, of all the recent high-profile cases where free
speech has been at issue, that of the London-based hatepreacher Abu Hamza is the
only one where I feel a criminal conviction was justified. Not because he was a
Muslim rather than a Christian, a Jew or a secular European. No. Because he was
guilty of incitement to murder. This is the line on which we must take our
stand. Facing down intimidation, backed by the threat of violence, is the key to
resisting the creeping tyranny of the group veto. Here there can be no
compromise.