It probably bugs me the way it does, because this "signal" has nothing to do with the contents or the usability of the web site (unlike speed, validity of HTML or, well, content itself), but is purely a "we just think you should do X" situation.
I would definitely prefer to use a site that supports HTTPS over HTTP. For personal safety reasons in addition to privacy and general welfare of the web.
If you're searching for something and roughly the same content is available at safedomain.com vs. notoriouslysketchy.ru, I'd think you'd prefer to be shown the former above the latter. I don't see how this is much different.
HTTPS is relevant to the content because it will ensure that Google's search results direct users to the same content providers seen by Google's web crawlers.
