Your religion might say killing a doctor who performs abortions is acceptable. Their religion might say killing a cartoonist who mocks their prophet is acceptable. In both cases you're saying murder is acceptable because your religion says so. That's pretty much textbook religious extremist.
Well, I don't see them as equivalent. Teller was providing a public service, giving substance to the law of the land (having the freedom to choose a medical procedure is meaningless if no doctor will perform it). The cartoons only have "freedom of expression" at their disposal which does not apply to corporate airwaves (not saying I agree with this, just stating the facts), and the laws about freedom of expression are not universal (the US is the only country I know of that has upheld the idea in court -- other countries at most claim it, even in the face of obviously contradicting laws.)
While the murders are equivalent from the point of view of the number of victims, the justification for killing Theo-Van Gogh was just vacuous, whereas the justification for killing Teller makes the crime far, far worse. I can go make a Muhammad cartoon anytime I like to fill in that void, I cannot suddenly go perform abortions to fill in the void left by Teller.
As Ayan Hirshi Ali stated, in order to fix the Muslim attitude towards depictions of Muhammad, you can just have *everyone* actually engage in it. The weight of the world opinion is not trivial and would give them pause to think. I think her analysis is correct. For the abortion issue, there is no changing those people's minds. Even if there was a pervasive education campaign, whatever remaining pro-lifers there would be would always be the most radical and would still carry out murders of doctors no matter what their demographic.
(You can't accuse me of being lead by my religion, because I am atheist.)