Both sides of the issue make both rational and emotional arguments in their cases.
Some see this as a civil rights case. Others see it as a religious rights case. Still others see it as a case of the Tenth Amendment and states' rights versus federal authority.
On March 26, 2013, the US Supreme Court heard oral arguments on both sides of the issue in regards to California's controversial "proposition 8". Proposition 8 is no longer a referendum but a ratified amendment to the state's constitution.
The arguments could leave you confused as to which way several of the justices leaned after hearing the case. Justice Kennedy issued the hardest questions on the Article III authority of the US Supreme Court to even hear the case, as though he is posturing to posit that it is a matter bet left to the individual states and not a matter for federal authority.
The decision will be a close one. The outcome is indeterminate. The court opinions on this case aren't scheduled to be finalized until June. The DOMA case to be heard on the 27th follows a similar schedule.
You can hear the audio file of the arguments here (download or stream from source it player doesn't appear below) or read them here:
Hollingsworth v. Perry