Morally I have no issue whatso ever with the death threat.
On a pragmatic basis? For a threat to deter behavior the other party must believe you have the will and ability to act upon it. If they call your bluff and you can’t/won’t do anything about it all you’ve done is make yourself look weak. They both know Charlotte doesn’t have it in her to kill him; and that death threat didn’t deter her in the least. Bojack is also too impulsive and hedonistic to act rationally even if she was willing to send him to the glue factory. I’d say she’d need to break his leg at a minimum to actually scare him off.
So if you understandably want Bojack to stay the fuck away from your daughter but you don’t want to go jail and you want to keep it off record what are your best options?
I don’t think it was necessarily meant literally, or meant to be understood as such.