There isn't a way to completely toggle it off, however you can toggle off portions of the feature. Under expansionsettings.gd (or in the Constants mod if you prefer editting it that way), look for "uniqueslavesautopartyconsent" and toggle that to true. That disables the consent system for all unique characters (basically by having them autoaccept everything).
Having the whole system toggled off is something that's feasible but it isn't in place currently. However, if you hit them with an Entrancement spell before talking to them, it should drastically increase the chance of them consenting.