I don't think people with BPD are "monsters". Most of us have had difficulties in our lives, and apparently we have more trouble controlling our emotions than most people do. Sure, it can cause interpersonal problems, but so can many things. It doesn't make someone "bad".
I definitely believe that a person with BPD can have long-term, successful relationships. It depends mostly on the individual and their personal experiences. I've personally been in several relationships that lasted for quite some time, although I wouldn't call them great successes. Still, that applies to a lot of people with or without a diagnosis.
Now, I am pretty much a hermit, but it's only partly due to BPD. I just find it too difficult to socialize for a lot of reasons, plus I'm out of practice lol. It's just me and my kitty.
Sending you hugs.