You do give your consent, its in the terms and conditions that you signed up to. If you are that bothered, just get a third party router which can't transmit BTwifi.
You miss the point entirely. Why should I have to take avoiding action? The terms and conditions (I bet you don't read them all either!) also say that I can opt out if I wish. But I am unable to do that even by following their instructions on how to acheive it to the letter.