There are Brexit options with an NI relationship that the DUP can back, and options that they will vehemently oppose.

There are Brexit options with a customs union that the UK can end unilaterally, and options where it can only end via a joint agreement.

There are options more like Canada, and options more like Norway

The second vote is not whether Brexit should be frustrated, but whether the particular version the government ends up with is one the people wish.

Now certainly my first preference would be to call the whole thing off. But my second preference is for a Brexit that does as little damage to the UK as possible.   So for example I would prefer just about any 'deal' Brexit to a 'no-deal' Brexit. That second preference is not in any way about frustrating Brexit.