The way the two major parties control the presidential debates is a perfect microcosm of how political debates are restricted in general. Though typically shrouded in secrecy, several facts about this process have recently come to light and they are quite instructive.
The right to vote includes the right to vote for, and hear from, the candidate or issue of one's choice. Third party and independent candidates in many states have to overcome restrictive laws in order to get on the ballot. The exclusion of third party candidates from debates silences their ideas that differ from the dominant two parties and prevents Americans from hearing about the platforms of all the candidates on the ballot.