Political speech is a core First Amendment value. Citizens United had nothing to do with contributions to campaigns. It invalidated an odious provision of McCain-Feingold that prohibited criticsm of candidates prior to elections.
"
In the 2008 election season, Citizens United the PAC sought to broadcast TV ads for a
video-on-demand film criticizing presidential candidate Hilary Rodham Clinton, but doing so would violate the 2002
Bipartisan Campaign Reform Act (known also as the McCain–Feingold Act), which barred corporations and unions from paying for media that mentioned any candidate in periods immediately preceding elections.
Citizens United challenged the law, suing the
Federal Election Commission (which
sets campaign finance laws and election rules), and the case
made its way through lower courts until an appeal was granted by the U.S. Supreme Court.
In a 5-4 ruling, the Justices declared unconstitutional the government restriction on “
independent” political spending by corporations and unions, and determined the anti-Clinton broadcast should have been allowed. The decision overturned
century-old precedent allowing the government to regulate such spending. As a result,
Citizens United has greatly affected the way corporations and unions can spend on elections (more on that below)."
http://reclaimdemocracy.org/who-are-citizens-united/