Final answer:
Factions threaten the stability of a republic by promoting self-interests and can lead to tyranny; historical incidents like the Whiskey Rebellion demonstrate these concerns. The republican system is designed to mitigate these dangers by preventing majority factions from easily unifying against minorities.
Step-by-step explanation:
Factions are considered dangerous to the republican government because they often promote their own interests over the common good, threatening the unity and stability of the nation. The fears regarding factions are rooted in historical incidents like the Whiskey Rebellion, where Federalists saw a need to demonstrate government strength, while Republicans viewed the response as potentially tyrannical. James Madison and others believed that the republican system could help mitigate the power of factions by making it difficult for majority factions to easily unite and oppress minority interests due to the variety and number of different interests in a large republic.