Proposition 8 - Breach of civil rights?

From Wikipedia:
Proposition 8 is a California State ballot proposition that would amend the state Constitution, to define marriage as a union between a man and a woman, overturning a recent California Supreme Court decision that had recognized same-sex marriage in California as a fundamental right. The official ballot title language for Proposition 8 was "Eliminates Right of Same-Sex Couples to Marry". On the day after the election, the results remained uncertified. With 100% of precincts reporting, the vote was 52.5% in favor of Proposition 8 and 47.5% against, with a difference of about 504,000 votes;[1] as many as 3 million absentee and provisional ballots remain to be counted.

So there you have it. Majority of voters decided that a marriage should be a union between a man and a woman and a union between homosexuals can never be turned into marriage. Though I do not understand all the ins and outs of this proposition, I have some views on gay marriage and voting to ban gay marriage.
How come millions of heterosexual people get to decide what homosexual people can and cannot do with their life? I see this as a civil liberties issue. What I do with my life should never be dictated by the government. If you dont believe in gay marriage, fine, keep it to yourself. What gives you the right to decide? I liken this treatment of gays to the way African Americans were treated. They were disenfranshised, treated as less than human, not allowed to run for office, were segeregated. It might come across as a very radical comparison but in some ways it rings very true to me. Marriage is a fundamental right of people.
Why was a marriage defined as a union between a man and a woman? Was it because when the constitution was written there was little knowledge about homosexuality?
If the constitution did not define marriage as between people of the same sex also, I believe it is because the idea that someone could be gay did not exist. Since the constitution was written so long ago, should there not be a revision to accomodate modern ideas? If right to own guns, right to free speech etc can be added later, why not redefine marriage?

As an aside - When I was reading about this proposition and history of the gay movement in America I came across this news report on the fox news website. So you can stop being gay by praying? Really? According to Wikipedia:
The term is used to refer to "an enduring pattern of or disposition to experience sexual, affectional, or romantic attractions primarily to" people of the same sex.
Being homosexual is like being female or male. Can you stop being female by praying enough? How many hours/days/years will it take for me to become a man?
Can we expect religious preachers and influential people to be socially responsible and not spew such nonsense?