I actually think I see the problem here. I should say “illegitimately absurd” instead of “absurd.” I will try to clarify my point.

So are you saying that the mere fact that a conclusion is “absurd” is enough to show that an argument fallacious?

Sometimes something that looks absurd will be proven by a valid argument. Being absurd is not necessarily good reason to reject the conclusion, but it is likely to show that the argument is inadequate. The absurd conclusions I discuss here are basically those that lack the extraordinary evidence required. (My point is that extraordinary conclusions require extraordinary evidence.)

To be fallacious is not the same thing as to be false or invalid. If an argument is fallacious, it might still have a true conclusion. It is merely not good reasoning.

If that’s the case, then why do you say: “If we find it very important to argue against someone’s conclusion, then we can do so, but we should first argue against one of the premises”? With the example: “A correct objection to the abortion argument is to challenge one of the premises”? This seems to go flat against what you said previously.

Why is this a contradiction? Why can’t we do both?

Rejecting a premise is important, but sometimes we aren’t sure which premise to reject. Sometimes an argument has plausible conclusions and an implausible conclusion. We can be uncertain that the premises are true and almost certain that the conclusion is false. The argument of this kind can be valid, but should still be rejected for being overly ambitious in a similar sense different from the other “overly ambitious” arguments discussed.

In this case we should still cite evidence against premises, but we should make it clear that we don’t know which premises (if any) are false. For example:

1. Many people have “past life experiences” that provide insightful information.
2. Either past life memories are caused by past lives or dreams.
3. It is very unlikely that a dream lead to such insightful information.
4. Therefore, some people probably have past lives.

I agree that the premises are all plausible (they seem to be more likely true than false) and we don’t know which premise is false. There might be other explanations for past life experiences, or it might be false that dreams can’t give insightful information. I don’t want to have to reject either premise, but the premises are too uncertain to lead to the absurd conclusion that “some people probably have past lives.”

So are you saying that the mere fact that a conclusion is “absurd” is enough to show that an argument fallacious?

If that’s the case, then why do you say: “If we find it very important to argue against someone’s conclusion, then we can do so, but we should first argue against one of the premises”? With the example: “A correct objection to the abortion argument is to challenge one of the premises”? This seems to go flat against what you said previously.