The only way to fix that (short of rearranging how meta site URLs are set up, which is planned, but keeps getting pushed back by more pressing things) is to force the link to go to HTTP only... which isn't great.
We do not officially support HTTPS on our sites, even though most of the time it will work. Browsing through HTTPS is a choice at this point, so quietly forcing you back to plain HTTP feels worse than forcing you to make the informed "do I want to continue or do I want to bail?" decision. So if you're running that way anyway, clicking past that warning is probably gonna just have to be the price you pay for the time being.
Hold on a sec, I took a closer look at the code, and it looks like we're already linking to the plain HTTP version (gonna need to fix that one up once we go to full SSL support for sure). Are you running HTTPS Everywhere or a similar addon that forces all connections to go over HTTPS? Everything I said above still stands in the general case for the links that are already protocol-relative, but now that I've looked at the code, I don't see how we're creating what you're seeing.