In general no major changes should be made to a paper after acceptance unless either requested by the editor or, if suggested by you, approved by the editor. There are of course trivial changes and there are major changes that can result from making removing materials in a paper. When a paper becomes accepted, it is considered ready for publication by the editor. If you then make changes to the paper (apart from correcting spelling or grammar) you need to communicate these to the editor and make a good case for why you need to make them and how you can ensure they do not alter the content and more importantly the basis for your conclusions. The reviewers have reviewed the paper with all the information included and in the worst case your paper may not have been accepted were not all of it there.
So making significant changes after acceptance is not to be toyed with and consulting the editor is necessary.
The problem in your case lies, as pointed out by dgraziotin, in that you need to shorten the paper after acceptance which is normally considered too late. On the other hand, if the editor asks you to do so, then I would assume the editor will see to it that the reduction does not significantly influence any vital parts of the logic and reasoning leading to your conclusions. In such a case you will need to follow instructions, the responsibility for accepting the paper with the final revisions still lie with the editor and you have not done anything unethical or wrong. I will, however, say that the order of matters seems jumbled within the organisation of the conference peer review system.