As others have explained, there is no security provided to the network by non-mining full nodes.
It started with Ver's tweet...
Of course, I'm not a twit, so perhaps I am merely ignorant here. Is there some Tweet made on the part of Roger Ver which you are claiming has started the instances of people pointing out that non-mining entities have no actual power on the Bitcoin network? Because that is what it looks like you are claiming. Would you be a good sport and post a link to this alleged tweet that started it all? Thanks.
I have not seen this argument being used by almost any BU supporter until Ver made the following Tweet:
Only a node that is mining is a true full node. The rest are just slowing down the propagation of blocks between the real full nodes.