The "grave danger" that the author is talking about is the danger of atomic weaponry
Explanation:
"Preliminary Statement of the Association of Manhattan District Scientists" was a 100-page report written after the atomic bombings in Hiroshima and Nagasaki.
The "grave danger" that the scientist is talking about in the article is the dangers of atomic weaponry. The article talks about the consequences that wrong decisions of leaders may have on its nations.
The disagreement that was most influenced by the renaissance idea of humanism was The indulgences.
The church used the indulgences as a way to get more money to the church, rich people would give land and big amounts of money to parishioners. Luther was strongly against it and for him, the indulgences were the last straw.
