Why did the Citizens United majority reject limits on speech based on a speaker’s corporate identity?

In Citizens United v. Federal Election Commission, the Supreme Court majority rejected limits on political speech based on corporate identity primarily because it viewed such restrictions as an unconstitutional burden on the First Amendment right to free speech.12

The Court’s reasoning included the following key points:

• Rejection of Identity-Based Discrimination: The majority held that the government cannot assign different free-speech rights to speakers based on their identity as corporate or individual, a principle previously established in First National Bank of Boston v. Bellotti (1978).1
• Marketplace of Ideas: The Court argued that suppressing corporate political speech interferes with the "marketplace of ideas" by preventing corporate voices and viewpoints from reaching the public, which helps voters identify entities hostile to their interests.1
• Lack of Compelling Interest: The majority concluded that the government failed to demonstrate that the ban was narrowly tailored to serve a compelling state interest. Specifically, it ruled that independent expenditures do not constitute quid pro quo corruption, and that concerns regarding shareholder protection were already adequately addressed by the institutions of "corporate democracy".1