It's just not relevant to the statement "I'm punching until they can't punch back" who threw the first punch.

I'm not sure I follow.

What I mean is that it makes no sense to say you're fighting a war to achieve peace if you're the one who started the war, breaking the peace that existed before then.

If peace is your goal, then the status quo was already in line with your goal. Starting the war contradicts your stated goal of peace.

Do I really have to spell all that out?

There are at least two ways to view this in the "war for peace" proponents' favor, I think:

First, it could be that you believe that war is already happening. In this case, Israel and other opponents of Iran might think that the status quo was a shadow war, and they are just continuing the war in a way that is to their advantage.

Second, even if peace technically exists at the moment, one side might believe that the other is moving toward war, and if allowed to complete preparations, will be significantly harder to overcome when they start a war in the future. In that case, preemptive war might be thought to engender peace in the medium or long term.

We don't have to agree with these casus bellis to acknowledge that they are at least superficially reasonable justifications, presuming they fit the facts.

Right. Only problem is, I wouldn't usually take into account hypotheticals that don't match reality. And neither would any reasonable person.