Problems with Character Talking

[Hemalurgic Headshot he/him]

So I've been working on some fantasy, but I've run into a dead end, or at least some rocky terrain.

So I have this character who is a slaver. He's real nasty and curses and scowls, spits, and whacks people with sticks. The problem is that I need to turn him completely around. He is speaking to a crowd of buyers for his slaves, acting like a perfect salesman. I just can't get it to click, him speaking persuasively and not negatively. Any suggestions, favorite ways to write salespeople, etc.

[Tsidqiyah he/him]

When we say he needs to turn around is this just for the block? or does he have a change of heart and his personality change?

For the first  it may be out of place for him to change like that unless you have already built into the character the public vs private faces. i normally would include the assistant who handles the PR stuff and the slaver handles the money stuff. 

The second direction (change of heart) generally requires some sort of epiphany moment, or a powerful motivation to change.

As for salepeople i like the ones who truly appear to believe in their wares, "My slaves are better then yours and no matter what you say, i'm still right." Sort of direction

[Yezrien]

Yeah, a persuasive salesman is one who knows his audience. Who are the buyers? What are they going to use the slaves for? Have the salesman explain, with ridiculous enthusiasm, why his slaves are just what you're looking for!

And to push the sleaze, he can try to pass off his atrocities as positives. When he trots out the more broken, despondent slaves, he can call them "docile." Since he's practically starved his slaves, he can call them "low-maintenance." Stuff like that. 

[manukos he/him]

he could have an aggresive marketing policy , like: "what are you standing there you worthless idiot dont you see how fine these slaves are " 

also if you are interested in creating a story i highly recomend the 10th season of the  writing excuses podcast feturing Sanderson himself 

Edited January 20, 2017 by Manukos

[Hemalurgic Headshot he/him]

That's great! Thank you so much. Let's see if this goes well...

[EthanBassett he/him]

I think the key here is motivation. Your problem is that it doesn't feel right for him to have both sides, but I think that being good at selling slaves is bad in and of itself. If his motivation for being professional lies in making money off the trafficking of people then you should be fine.