Part of freedom is the ability to do what you want so long as it does not harm anyone else. Sports betting does not do harm to anyone, so those that want to participate should be able to do so because it is their money and they should be able to spend it however they choose. Legalization would allow for better regulation and increased betting fairness like that at racetracks. It would also allow for income from taxation, which this country sorely needs.
Sports betting should be legalized across the world. Governments can tax the proceeds and earn extra revenue in addition to giving bettors another option for gambling. Many states have legalized gambling at casinos, so why not add sports betting as well? As with any casino, there can be support groups for people who feel they are addicted to gambling.