This is close to your request, I think close enough. In it, Steve's moral code is very much anti- at the beginning. It's a long slow story about Steve, religion, internalised homophobia and shifting viewpoints. It may make you furious at times, but it's an excellent story, one that might have been a failure in the hands of a lesser writer.

Not About Superheroes (A Private Little War) (http://archiveofourown.org/works/747827) by Anna Fugazzi.