I could go on about the CC Wiki license that says, technically, this is allowed - their content is still on the site after all. So let's put aside the technical aspect and look at the social aspect.
I wouldn't go around digging up everything everyone writes and ends up deleting, of course, but you aren't doing that.
You're just showing a deleted answer, which you wanted to do to highlight the portion of the deleted answer that shows it was deleted by the author. You did this to strongly assert this with physical proof that goes beyond just word-of-mouth that the post was self-deleted, and not moderator deleted.
Like Aleadam and Changeling, it would possibly be seen as more respectful, so to speak, to blur out the content of the answer or the answerer's name - the fact it was self-deleted generally means that the author doesn't want the post to be seen. But I wouldn't call it bad behavior to neglect to do so, not in a scenario like this where your intent was clearly to focus on a different element altogether.