In the past I've been told to hire specifically for the personality trait of being willing to push back hard. Though stubborn people might be difficult sometimes, I really appreciate their presence when requirements are unclear or unrealistic.

With that said, code quality, F/OSS license policies, and testing should be something the whole team talks about and comes to an agreement on. There's a big difference between pushing back and failing to meet the team's basic standards, and at a certain point it becomes a performance issue.