The post was edited to make it less argumentative. The Stack Exchange model was designed to promulgate laser-focussed answers to specific questions, not a site for arguing and debate. Unnecessary rhetoric and protracted arguments typically just makes finding the actual answers difficult if not impossible.
As an answer that is not only highly-voted but also accepted, it has not only demonstrated value, but it is also representative of the site. Simply editing it to make it fit with our model is far preferable to deleting it.
I am not the one who locked the post, but as you have rolled back exactly the same edit in the past, I agree with the decision. It had been suggested to you earlier to bring the matter to meta for a community discussion so you could better work within community norms, but in the intervening year you chose neither to do so nor to make any attempt at improving your answer.
Even if the post was unlocked, you still would not be able to delete your answer because it's already been accepted. Unless you can convince the question author to revoke his accept, deleting can only be done with the aid of a moderator.
And so far, your only argument for deleting is that you don't like the idea that it's been edited. The edits don't in any way affect the actual answer, it merely makes it less argumentative and more suitable for the site we're trying to build here; this is something that any user can do, and in many cases is expected to do, and is a fundamental part of the Stack Exchange model. From the help centre:
If you are not comfortable with the idea of your contributions being collaboratively edited by other trusted users, this may not be the site for you.
The fact that you consider the edited lines to be "the most important part" of your answer suggests you don't really understand how the Stack Exchange model works. Similarly, rather than attempting to discuss the issue here in any constructive manner, you simply demanded that exactly one of two options be enforced: Reversion, or deletion. However, until you can demonstrate that either,
- The community feels the edited-out lines actually provide any value to the answer and it's ability to answer the question, or
- The community feels that deleting a highly-voted and accepted answer actually has any benefit at all,
then neither option seems viable, and as a moderator there really is nothing I can do about it.
I am more than happy to unlock the post so the community can continue to work with it, but if you insist on simply reverting the edit with absolutely no regard for anything else, it will simply be locked again and more drastic measures may need to be taken.