Your heart is in the right place, but this is a fundamental misunderstanding of the disorder. There are actually a lot of fundamental emotional and cognitive problems in people with BPD, usually due to severe childhood abuse, and it requires very specialized therapy to improve this.
Unfortunately, there is a severe shortage of qualified professionals for this and way too many unqualified quacks pretending they can treat any and everything.
In other words, asking someone with bpd to stop being a raging bitch is like asking a fish to stop breathing water
More or less. You really should only date someone with BPD if they are in treatment (or have been treated), they are trying their best, and you are willing to deal with these issues when they inevitably arise. BPD never goes away, but it can be mitigated a lot. If that is too much to ask, that's fine. Just date someone else then.