The cause of the problem is that Google is not seeing the newly added X-Robots-Tag because it's not re-indexing the page.

Removing the ban from robots.txt and letting Google fetch the pages with their headers does remove the pages from the results.

Sitemaps don't have much to do with indexing or rankings. You could remove URLs from your sitemap or even remove your sitemap entirely without hurting your SEO.

• A sitemap isn't needed to get the pages on your site crawled and ranked. Googlebot will crawl your site from the home page even without a sitemap.
• Sitemaps can occasionally help Googlebot discover pages on your site that are not linked from other pages. Googlebot will crawl that page but usually it will decide not to index or rank it. To get pages indexed and ranked well, they really need to be linked from other pages.
• Google doesn't use several fields that can be added to sitemaps. The changefreq and priority fields are just ignored. Googlebot comes back to crawl URLs based on how popular they are and how often Google has seen them change before.
• The biggest benefit of Sitemaps is providing extra data to you in Google Search Console.
• Google also uses sitemaps as a signal as to your preferred URLs. If you do have a sitemap you should ensure that it is clean.
  • No duplicates
  • No error URLs
  • No redirecting URLs

For more information see The Sitemap Paradox.

robots.txt

User-agent: *
Disallow: /

this will block all search bots from indexing.

for more info see: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=40360