There are a couple things wrong with your argument that I would like to correct. First, falling in love is a choice. When you "fall in love" you become infatuated with your significant other, and you will eventually fall out of love.
Second, yes, the government shouldn't tell them whom they can and cannot marry, but we shouldn't even have this problem! Homosexuality is not natural. Just look at the male and female bodies. They are obviously designed to couple. The natural design is apparent. It is not natural to couple male with male and female with female. It would be like trying to fit two screws together and to nuts together and then say, "See, it’s natural for them to go together."
In addition, political protection of a sexual practice is ludicrous. I do not believe it is proper to pass laws stating that homosexuals have 'rights.' What about pedophilia or bestiality? These are sexual practices. Should they also be protected by law? If homosexuality is protected by law, why not those as well?