Browser vendors have already inserted themselves into this role by selectively blocking Flash, messing around with how certificates are presented by the browser to imply certain things ("green lock == safe") when no such implication can be made, blocking and/or allowing ad blockers, etc.
Maybe you're too young to remember when everyone had to update their Flash installations every week because that product was improperly sandboxed, so you think that the issue was purely battery related. Blocking and restricting flash is as much about security as battery, more-so in my opinion.
But OK, let's compromise -- rather than preventing connections to Wordpress sites, maybe they could draw a big red line through a picture of the Wordpress logo, and then perhaps warn the user that this site is or soon will be serving malware.