[fiddlosopher]

If you don't want pandoc's fenced divs, just choose a markdown dialect that doesn't support them: e.g.,

    pandoc -f html -t gfm https://www.fsf.org

Or, to get rid of the divs and spans altogether, disable raw HTML as well:

    pandoc -f html -t gfm-raw_html https://www.fsf.org

[rurban]

those have even raw div's then.

    ...
    </div>
    <div id="sitemap-2" class="yui3-u-1-2 first">
    ...

[fiddlosopher]

As I explained, if you don't want raw HTML, use the second form:

  pandoc -f html -t gfm-raw_html https://www.fsf.org | grep div

gives no output. (If you get different results, it is possible that you are using an earlier pandoc version and something changed in this regard.)