The term is pejorative but has been in common usage to discredit someone.
I don't think anyone who uses it means to denigrate children born out of wedlock.

I think, upon further reflection, that maybe another term might be more specific such as
psychopathic, sociopathic, unreliable, destructive, disordered, damaging or disingenuous but none of these terms have the short bite to describe this form of behavior.

How about "jerk" although that's become too benign. I reject the term "evil" however because of it's religious connections.