I think it’s a legitimate question.
There are a couple of significant differences, though. The caretakers of the Jews (themselves, mainly) are not presenting them to be killed. Not that it would be right to do so, but they are being killed against their will.
In the case of abortion, we also assume that the unborn are being killed against their will, however, their “caretakers”, the pregnant women, are willingly participating in the murders.
Second, in Nazi Germany, there is absolutely no chance that the citizenry cound peacefully and in a democratic manner change the policy that is responsible for the Jew killings. That being the case, there is no other recourse but to resist and oppose by violent means.
Such is not the case with abortion. We, as a society, could easily stop (“legal” ones, anyway) abortions through peaceful means at the ballot box. I use easily in the sense that it would not take a violent overthrough of the government to accomplish it. As a practical matter…well…we’ve been advocating legally preventing abortion for years, and we’re not there yet.