Give the Confederacy her deserving freedom and end this war tomorrow!
—A Sympathiser cry

The "J. H. Childs Flag", a popular flag with the Sympathisers, made in early 21 BBY by Jonathan Henry Childs, a notable Sympathiser from the Republic of Westerland, to celebrate the young Confederacy

The "James F. Davidson Flag", another popular flag with Sympathisers, designed by Captain James Frederick Davidson, commander of the pro-Confederate Wekland State Guards
The Sympathisers (often nicknamed by Unionists as the Traitors, Confed Subjects, Confed Betrayers, the Enemy within the Gates, Rebel Wannabes, Zarkan Slaves, as well as the more simplistic insult of Cowards.) were citizens of the Union of Earth States who opposed the Union's war against the self-declared Confederate States of Earth.
Most Sympathisers held right-wing patriotic, nationalist and Libertarian views, most Sympathisers viewed the Union of Earth States as a left-wing, Globalist dictatorship, and the Confederacy as a right-wing, sensible, democratic nation fighting to defend her independence from the Leftist menace.
A universal view amongst Sympathisers was that of the illegality of the Union's war, the Union had invaded a neutral nation whilst trying to invade the Confederacy whilst they were attempting to peaceful negotiations, Sympathisers believed that all nations had the right to decide how they were governed, and to remove themselves from a political body they believed to be detrimental to their rights, interests, and well-being, and thus the Confederacy was legal by the right of self-determination.
The Sympathisers used Unionist anti-war and Confederate patriotic songs as rallying songs, one of the most popular being The Battle of Valandia, a song about the humiliating defeat of the Union Army in the early part of the war during the Valand Campaign, which many Sympathisers used as evidence that the decadent Union could not defeat the independent, and highly determined, Confederacy.
The most popular Confederate songs with the Sympathisers were The Bonny White Flag, the most popular national anthem, Valand, Great Land of the East, God Save the West and The Confederate Infantry Song.
Sympathisers were named as such because most held sympathies for the Confederacy, and wished for their own nation to abandon their efforts to restore Union control over the nations of Confederacy. However, many Sympathisers weren't outright Confederate sympathisers, some simply wished for hostile action to end and peaceful negotiations resume.
Most of the militaristic Sympathisers formed their own volunteer units with the Confederate military, for example the 1st (Union) Volunteer Brigade.
Despite earning the ire of Unionists, a significant number of Union citizens were Sympathisers, especially in the Union's border nations with the Confederacy, such as the Republic of Wekland, where Confederate sympathies were strongest.
In these border regions Sympathisers made up a larger portion of the population, and were thus able to go about their campaigns in relative peace, in more Unionist areas such as Nortalia Sympathisers were often abused by Union nationalists for their pro-Confederate views, or were imprisoned as traitors by the authorities.
Sympathisers were also sometimes arrested and imprisoned for treason without trial, Union nationalists viewed Sympathisers as little more than slaves of Jane Zarkan, the President of the Confederate States of Earth.
Go bow to your Rebel queen, you slaves of Jane Zarkan!
—An angry Union nationalist counter-protesting some Sympathisers
On the whole, however, Sympathisers were largely successful in their goal, many citizens in the Border regions refused to join the war, even after the Union government effectively forced them to with the passing of the Union National Conscription Act, following which they rioted, of the biggest riots being the Union City riot, there was extremely low morale and support for the Union cause in the regions, and the significant lack of support for the Union's war in the Union border regions may have contributed to the relative short duration of the war.
Under William Crest's Earth Empire former Sympathisers were heavily punished as traitors, even those who didn't outright declare their support for the Confederacy, and merely wished for peace, since William Crest viewed all Sympathisers as guilty of treason. The vast majority gleefully joined Elizabeth Zarkan's Imperial Kingdom of Zarkania.
Naturally, the "Sympathisers" obey me in the same way they obeyed my late cousin. It is, of course, right for those in servitude to kneel before their master.
—Elizabeth Zarkan giving a partial insight into one of her personal views on the Sympathisers, during a private conversation