論点 and 根拠: the issue examined and the grounds offered
Compare organizing three issues with a request to explain the grounds for an opinion. Read the question under discussion separately from the support for a judgment.
The issue under discussion
論点 (ろんてん) means an issue or point at stake. 「議論の論点を三つに整理した。」 describes organizing the discussion’s issues into three points.
「話を戻して最初の論点を検討しよう。」 proposes returning to the first issue to examine it. Organizing an issue is separate from reaching a final conclusion.
The basis for an opinion
根拠 (こんきょ) means grounds or evidence supporting a judgment. 「その意見の根拠を具体的に説明してください。」 requests a specific explanation of the basis for that opinion.
「根拠のない噂を信じず、記録を確かめた。」 says the records were checked instead of believing an unsupported rumor. The check is stated, but its particular findings are not.
What to examine and what supports a view
論点 identifies what is to be examined; 根拠 identifies what supports an opinion. Different grounds can be offered on the same issue.
Three points are the result of organizing this discussion. They are not a fixed count for every discussion, and organization alone does not establish a conclusion.
What is to be examined again in 「話を戻して最初の論点を検討しよう。」?
Show the answer and why
The first issue. It proposes returning to a point of discussion, rather than reporting that grounds have already been explained or a conclusion fixed.