Final answer:
In the given context, 'belaboring' means criticizing. It implies heavily focusing on the problems causing divisions between parties, which relates to the challenge of polarization where groups divide into extreme opposing sides.
Step-by-step explanation:
The word belaboring in the context provided means criticizing or discussing an issue to an excessive and unnecessary degree. The sentence suggests that instead of focusing on the problems which cause disagreement and conflict (what belaboring would entail), the two sides should look for common ground by exploring problems that they both recognise and which could unite them.
The challenge of polarization
When people or groups are divided between two extremes on an issue, the challenge that is occurring is called polarization. This situation can make it difficult to find common ground because the parties involved focus on the differences that divide them, often leading to heightened tensions and conflict.