Your assumption that by packing him off to Spain somehow sky will cripple BT. they have a very clear plan as far as I can see, offer sport for free in order to win over broadband customers.
All this "sky are against us" nonsense makes us all sound like Liverpool fans.
They are what they are, a tabloid sports news outlet that will always play up any news to the most dramatic effect.
No one is going to sign up for sky simply for the Spanish league with or without Bale. So him going to Spain doesn't really strengthen their already strong position over BT much.