you can’t not.

 We can't "not take a stance". It's just not one of the choices. 

In not taking a stance we are taking a stance that this particular thing is not worth taking a stance on, compared to all the things that we do take a stance on, and, that, in itself, is taking a stance. 

We can be honest about that. But we can't say "I don't have a stance on this one."