In this period populists, or demagogues were viewed as extremely dangerous to the power structure of Rome. It was a way to rouse the public to gain power, by-passing the traditional structure of the senate. Since the people could not directly vote, getting them on your side was primarily a threat of violence to those who opposed you.
And it wasn't uncommon to assassinate these guys when they started to look like they might get the people too relied up and before they stormed the senate.
Anyhow, that's why populists were probably modeled this way.
But Caesar and Marius were both populists... so why do populists hate wars?
In Rome, success in battle often equated to popular support at home.