Hey Loozinit, I see you're in western Washington. Me too. Seattle area.
Your huntin' buddies are 100% correct. Spit, or any water-based lube, isn't good in a hunting situation. The load has to be fired within a few minutes or it will dry out. Mebbe cause rust too.
But at the range, it gives nothing away in terms of ease of loading or accuracy. I use it because it's convenient, like no prelubing, no melting in hot weather or hardening in cold, and I don't have to carry extra stuff. Plus I can easily vary the amount with changing conditions. I wipe with spit too, for the same reasons.
My post wasn't aimed at you, but for newbies that might think they have to have a ton of stuff to shoot muzzleloaders. I promote keeping it simple, like ya don't need special concoctions for lubing, wiping, cleaning, etc.