Act 1: When I'm not paying attention, my friend says, "hey, do you mind if I go through your address book and contact all your friends and family and ask them to be my friend too? If you consent, say, 'what' or 'huh'"
Act 2: When I'm not looking, this friend goes through my address book and spams all my contacts with whatever they're selling under my name.
What would you advise me to do after that? You'd probably say, this person is not your friend by most definitions of the word, you should cut them out of your life and ask them to not contact you anymore.
To which I may say, but this friend is well connected, they might be able to get me a job in the future. (Although I've never gotten a job or even a lead through LinkedIn personally.)
What would you say to that? Probably something like, they're abusive and deceitful, whatever they have to offer, they'll probably damage your life more than they'd help you.
And that's why I closed my account and added a "delete on sight" filter for their emails.