All legacy content that is hosted using http protocol is, in fact, not secure. It's definitely not a bad thing to warn people.
Personally don't understand the heavy push to force https on everything and anything. The maintenance/time required to set up and maintain is not insignificant and is really quite pointless in many situations. Do you really need an encrypted connection to LOLCats?
If you only use an encrypted connection when you need it, then one can know that, well, you need it.
You have nothing to hide... until you do.