how do you open the heart chakra without loving everyone?

[Sacred Fool]

It's more like you see it's best you have a positive overall attitude toward everyone because you recognize that hostility/negative feelings won't benefit anyone.

For what it may be worth, I read that as pure yellow ray practicality and not nearly vibrating at a green ray frequency.  It may be this mis-identification which earns you the slammed door.  That is, people who can tell one from the other are looking for genuine green ray vibes and may have little use to mere good wishes.

Gulp!  I hope you don't ask me to try to articulate that difference.  It ain't easy.