You can just not connect the two.

If you're connecting them I suppose you want to use discord through battle net, so these permissions are needed.

• friends stuff to invite and chat with your friends
• server stuff to invite your discord friends
• profile stuff so they can show it to your discord friends while on battlenet

As for the advertising stuff, go through discord and battle net and disable everything you can. BattleNet is not selling anything discord isn't already selling.