Let's Talk About "Unconditional Love"

I’d like to have a discussion here on the topic of “Unconditional Love” ~ its meaning and implications with respect to controlling, unhealthy, abusive relationships.

I am hoping to gather input from all perspectives:

Believers ~ what is unconditional love? Please explain the concept and its specific application in cases in which someone is getting hurt ~ whether physically, emotionally or spiritually.

Unbelievers ~ is “unconditional love” strictly a religious ideal? Is there a secular version of unconditional love? How does unconditional love play out in practicality?

What about situations where the abuser is a close family member ~ say, a grandparent, parent, spouse, sibling or child? How does one show unconditional love for a person who hurts their own relatives?

I’d like to get the discussion started on this note: I used to believe wholeheartedly in unconditional “Agape” love ~ but now I’m not so sure. To quote one of my favorite skeptics (Uncle Ron ~ who once wrote to me at length on this topic):

“Unconditional love is good for babies perhaps, but not for adults who aspire to reason and responsibility.”

Whatever “Unconditional Love” is, I am now convinced it does not mean indiscriminate trust or naked vulnerability.

What are your thoughts?