Is it unethical to expect one's PhD students to work after graduation without compensation? Should graduates ask for compensation for work? My thesis advisor expects me to 1) write the paper rebuttal and 2) finish any remaining experiments by coming in on the weekends, for free. I am now working full-time in industry, and no longer being paid by him. Is this ethical?

Part 2 of my question:
I would be happy to do this if it had been my fault that we didn't submit my paper until the week I graduated. However, my history with this advisor has been:


1 year before Jan graduation date: We agreed that in 1 year I could graduate given the finishing of certain key experiments. He also insisted that I be here for the rebuttal of the paper after its been submitted.
During this year, we agreed that I was on track for this.
3 months before Jan graduation date: I brought up my Jan graduation again, and he protested saying it would take longer than I thought to write, submit, and wait for revisions to come back (different than being on track like we had agreed I was!) 
I of course was dissapointed that he didn't tell me this sooner, that I wasn't on track. I relented to a compromise where I graduate in March instead of Jan. 
Dec: All of the key experiments had been completed and I insisted on submitting in Jan or by the end of jan so that I could still be here for the rebuttal (3 months to write, submit, and get reviews back). He agreed that would be enough time.
Jan: He now wanted me to do several more, additional experiments for the paper. I tried, but the experiments were not going well. I kept trying to mention that the paper needed to be submitted. He relented, and we ended up submitting at the end of March.


Now, he doesnt even have the time to give me feedback on a draft of the rebuttal until after I put everything together (meaning I may be wasting my time on things that he will ultimately throw out or veto)

Therefore, I feel he has fanagled things so that he can get the most value out of me without regard for me as a person, and that includes this new period of being asked to do work with no mention of pay. Is this unethical and should I ask him to pay me for my work on the rebuttal?
You are thinking about this like an industry employee (which you are, so that's a reasonable stance).

Your advisor is thinking about this like an academic (which they are, so that's a reasonable stance).

Some perspectives:

Academic work is personal work and community work

You don't work for someone in academia as much as you work with someone. It seems like you are feeling a lot of conflict with your advisor right now, but I'd step back a bit and think about whose research this is. Certainly at some level your work benefits your advisor, but isn't it your own work, too? Do you not want to see your results published?

Is your advisor making decisions about suggesting further experiments that pushed your timeline beyond what you hoped because they are getting free work out of you, or are these steps to make the paper better and importantly to make it publishable (see below)?

In academia, it is normal to work on projects from a previous position; in industry it is not

Almost every academic will, at any time they move positions (including graduating as an undergraduate/graduate student, between temporary positions like post docs, and when getting hired as a professor and any moves afterwards) have some unfinished business at their previous place of work.

It's not reasonable to expect every research project to fall neatly into the academic calendar, conveniently finishing right at the conclusion, especially given the unplanned timelines surrounding peer review. Therefore, people tend to spend part of their time in their new position finishing up things from their past one, while being paid only by the new institution.

This gets "paid forward" in the future when the same happens during the next transition. A frequently asked question here at Academia.SE is some version of "which institution/affiliation should I list on this paper, new or old?" because of how often this happens.

Unpublished work is worthless to you and the academic community

Maybe your work is in a thesis in some draft form already, but all of the work you've done that isn't published is doing nothing for you or for academia. Maybe you're fine with that, because you aren't an academic anymore, but ultimately whatever funding agency funded your research and the university you worked for did so because they wanted you to produce published results, not just to give you the PhD title. If you think there is value in the work you've done, then that should be an incentive to get it into a form that can be shared.

On the other hand, you may decide that publishing is not actually of any benefit to you. If you don't feel intrinsic worth in the project, and if you don't plan any return to academia, then probably one more published paper won't mean anything tangible for your CV.

Given these differing perspectives...

I don't think there is any fixed answer. Should you do work for a past advisor without compensation? No. Should you collaborate with people you've worked with in the past to share your research with the broader academic community? Probably yes.

Ultimately it's up to you to define where those boundaries are. Personally, I would think it to be irresponsible to fail to follow up on basic authorship duties like responding to reviewer comments, editing manuscripts for submission, etc. These activities shouldn't replace paid employment, but they can be completed in a few free hours during a transition period. Coming in on several weekends to run experiments sounds like a bit much - maybe there is a compromise solution where you can train a new student to run those experiments, add them as a coauthor to the paper, and continue helping with the manuscript(s)?