Re: Why have it?
"Why do they even have this DB?" It's pretty hard to have a membership organization like a political party without having a database of the members.
"Did they get permission from the people to store their personal data?" Yes of course they did.
"... and let it be exploited by ANY politicians?" I'm sure they will have had wording like "to enable us to contact you to support our campaigns". And the members will have agreed to this.