This should be its own thread....
I'm not sure incite is that obvious - maybe actual psychic damage is, but I'd say the maneuvers are designed to be subtle otherwise everyone would know what a White Court Vampire is.
Hitting their High Concept: This is more of an OOC thing.
FYI: White Court Vampires are not hurt by Sunlight.
If the PC is a white court that feeds off pride and (s)he uses a maneuver to cause someone to be Prideful. it means an aspect related to their Hunger is now on the scene. Use a FP and invoke that aspect. Compel them to lose control and want to feed. This forces them to act in a way that is less subtle - they will want to Psychically EAT someone - which translates to kill them. This is pretty obvious.
There are other compels you could do. compel him to hit other people up with Pride because he loves the feeling of it. Suddenly there's a bunch of prideful people in the room arguing and a fight breaks out and now he's caught in the middle of it.
Maybe there's an important political person in the room and, because of his Prideful feelings, feels slighted by the Vampire. Now this person has it out for them.
Remember that every aspect is a double-edged sword.
Your GM should really be doing the compelling, though. But, as long as your character knows an aspect exists, you can invoke it. In fact, if you have a character aspect that would be related to it, I see no reason why you wouldn't get a FP to have a vampire want to start feeding on you. Seems like a complication to me.
I'd think that using another person's pride to get your own way in an argument would be difficult unless you're using reverse psychology. But, that's what White Court Vampires do: they manipulate people.
Once again, why is a fellow player trying to manipulate all the other Player's characters?
Edit: IF you want to learn more about a character, use Empathy to learn an aspect. If you have low empathy, rack up a few aspects in advance: contacts to gain info on them, Investigation, alertness. Maybe a few declarations. Spend a FP if you need, then roll empathy and make sure you have a high enough roll. Once you know the aspect, you will always know it. Part of the reason they are manipulating the situation is because your character doesn't know what they are. Once you know, it will be harder for them to do. Be careful though. They probably have high deceit. if they defend with deceit, they can give you a false aspect, so make sure you roll high enough. You should probably know if you succeed or fail, though.
In any case, I recommend you talk to your GM and the group if this is frustrating you. It really sounds like a group dynamics problem. All my proposed solutions are just to help you turn the tables on the Character and make the game more interesting. They shouldn't really be done as a passive aggressive tool to screw over the player in question. All compels are negotiated anyways, so you'll have to talk about the problem in any case. It might just be a good way to bridge the subject if you start compelling those aspects against the Vampire (assuming they are a vamp).