Thomas Jefferson's supporters argued against neutrality because they believed that the United States had a moral obligation to support France, which was fighting for liberty and democracy in Europe during the French Revolutionary Wars.
Jeffersonian Republicans, as they were called, saw France as a sister republic that had been inspired by the American Revolution and was now fighting against a monarchical coalition of European powers. They believed that the United States should stand by France as an ally in the struggle against tyranny and absolutism.
To Jefferson's supporters, neutrality represented a cowardly and opportunistic stance that was unworthy of a nation founded on the principles of liberty and democracy. They believed that the United States should be actively involved in promoting these values on the world stage and that supporting France was a necessary step in achieving this goal.
They also saw parallels between the United States and France in terms of their shared histories of fighting for independence and freedom. They believed that the American Revolution and the French Revolution were part of the same struggle for liberty and that the United States had a duty to support France in its own fight for freedom.
Overall, Jefferson's supporters argued against neutrality because they believed that the United States had a moral obligation to stand with France in the struggle for democracy and freedom in Europe, and that doing so was in the best interests of the United States as well.