It's also possible to right laws that allow for gay "marriage", but don't force, say bakers, to bake cakes for gay weddings. The way things actually play out suggests this isn't actually possible in practice.
"In one of a dozen or so countries where X was done, Y also happened" isn't even terribly strong evidence for "it's not possible in practice to do X without Y also happening", let alone "it's not possible in practice to do anything in some reference class including X without something in some reference class including Y also happening".
For another data point, there is at least one major European country where doctors are both allowed to perform abortions and allowed to refuse to perform abortions and the situation hasn't changed much in either direction for decades.
Performing abortions requires special skills. Thus it would make no sense to force doctors who aren't trained for the procedure to perform it.
Over at Scott Adams' Blog you can find a very fine example of using the 'Rationality Engine' to solve the social problem of assisted dying.