The free-soil idea was put forth by a single-party called 'The Free-soil party'. The party raised objections for spreading slavery towards the West. They had one motive to keep the slavery out of Mexican lands.
The radical northern invaders by acquiring new territories over the West established slavery in those acquired lands. This idea was favorable to some of the north racists, who did not want to compete against the black laborers.
It is an opinion rather than a fact because there is no data to support that all service members and veterans have challenges when they return. There are no factual statistics or data to back up this claim so therefore it is an opinion