can my paper be excluded from the conference proceedings after attending and presenting? I received a very weird email from an international conference committee, stating that their society (who organised the conference) reviewed the content of my paper and finally decided to exclude it from publication in the proceedings because my ideas did not reflect the society ideas and methods.

This is after they accepted the final edit of my conference paper, about 8 months after the end of a 10 day, very expensive conference. The book they are publishing is not a selection of papers, but the only proceedings which records the facts, topics that were discussed and people that were at the conference.

The paper topics were determined when the initial abstracts were submitted. There were no conditions specified at the time of registration, therefore, as for other general international conferences, registration, acceptance and oral presentation means being part of the proceedings, if not otherwise explicitly specified. 

Can my paper and thus the record of my attendance and presentation be excluded from the conference proceedings? Can they discrimate against authors based on the society's views?
I find your arguments very compelling and persuasive (except the one about “generating money losses”, which I think is not really the point, and isn’t something I’d advise you to focus on, although it’s understandable that having incurred great expense to attend the conference would add to your sense of outrage). If the conference website, correspondence with the organizers, and other official conference materials led you, and would lead a reasonable person, to believe that your paper will be published in the conference proceedings, then it seems pretty clear-cut that the organizers are guilty of a serious misrepresentation, and, under normal, circumstances, their behavior would be completely unacceptable.

The only explanation I can think of that would make for a legitimate reason to exclude your paper from the proceedings would be if they discovered that your paper is outright fraudulent or involved some serious unethical behavior on your part. Just saying your paper “does not reflect the society ideas and methods” isn’t nearly enough of a justification to make such a drastic move sound acceptable. (But I assume there are additional details that would shed more light on what’s going on here, although they may not change my conclusion.)

As for what you can do, it’s hard to say without more background details about your field, the people involved, what they find wrong with your paper, your professional status, etc. But certainly I think it would be quite reasonable on your part to raise a fuss and complain about this seemingly unfair treatment, and ask for the decision to be changed.  Some people you might want to involve could be your department chair, other colleagues you are on friendly terms with, your advisor (if you have one), people you know who attended the conference, the chair of the organizing committee, and the publisher in charge of the proceedings volume. I think it’s quite possible that once this decision is scrutinized by enough reasonable people with some sway, you will see justice done.

Good luck! Hope you get this sorted out.