No. He was trying to kill you. Imo any amount of force and any target is justified in that kinda situation. Even if you managed to slice off his balls it'd be justified imo. Granted, if he disengages and you feel safe, then you should stop; I'm just saying that, in the moment, I'm not sure I would have felt safe enough to let him disengage.
Edit: the throat is far more vulnerable than the belly. Smaller target, but significantly easier to damage something in a fatal way.
You forget about furry porn. Furries draw porn because we like it, not because we make money at it (but money allows those of us who do it to actually potentially live off it).
Edit: or to put it another way, someone drew furry porn and discovered they could make money doing it, not the other way around.