They are Phishing. They invite everyone to a group, then invite them to Battle-net friends, if you accept they get your email, with your email they will send you Emails trying to be "Blizzard" that will probably direct you to a Phishing site were they will try get your password, then take your account..
Tell them to fk off and report them, they use account after account. They get banned they make a new character and keep inviting people until more accept. They don't target botters, they target anyone leveling hoping for a newbie.