It is morally right to break the taboo based on the I am Spartacus principle alone combined with even the tiniest bit of respect for the principle of free speech. I'm sorry if you believe that free speech isn't worth fighting for, but I hope you can at least understand where we are coming from.
I do believe that free speech is worth fighting for. But I don't think that all speech is worth fighting for.
This taboo isn't dead; it's dormant. The religious commandments supporting it are still there in the hadith [...]
That's kind of irrelevant. Jewish and Christian taboos against lending money at interest are well and truly dead, despite the commandments supporting them still being very much there.
So, my question to you is simple: what is the criteria you use to determine which taboos of Islam must be respected by non-Muslims?
I'm going to leave aside the objection that there is such a monolithic entity as "taboos of Islam", on the grounds that I know what you meant.
To me, this isn't the interesting question. Taboos do not demand respect, people demand respect by virtue of being human. Given that I live in a multicultural society which contains a large number of ethnic groups each of which has its own cultural beliefs and practices, what is the best way to respect those people and simultaneously protect the rights and freedoms of everyone in that society?
A taboo against drawing some historical figure is, by itself, completely harmless. Moreover, it is a right that deserves to be protected; the government should not be in the business of mandating portraiture.
The point where it becomes harmful is the point where some in that community might seek to impose it on others. Up to that point, I would not go out of my way to break the taboo in their face. After that point, those who seek to impose the taboo on others, and only those people, deserve to be insulted.
So if you can find where the half-dozen-or-so people who hold the "behead those who insult Islam" signs at rallies (who seem to disproportionately attract TV cameras) live, I would be part of a "Draw the Prophet" event to be held outside their houses. I strongly believe in insult as a form of protest. It is a fine tool, not a blunt instrument to be wielded indiscriminately.
Did that help?
Incidentally, if you think that's weird, try this on for size. Here in Australia, there are some indigenous peoples who have a cultural taboo against depicting or naming people who have died. How do you "respect" that?
Well, one compromise that we have is that we run a content warning ahead of any TV show which is specifically targeted to Indigenous Australians. Does that seem so unreasonable?