Pacquiao, a devoted Christian who boxing enthusiasts want to see fight rival Floyd Mayweather, said Obama is wrong on gay marriage and cited the Bible for his disagreement with the president.
If a man lies with a man as one lies with a woman, both of them have done what is detestable. They must be put to death; their blood will be on their own heads, Pacquiao said in an exclusive interview with examiner.com, referring to Leviticus 20:13.
God only expects man and woman to be together and to be legally married, only if they so are in love with each other, Pacquiao, who is a congressman in his native Philippines, continued. It should not be of the same sex so as to adulterate the altar of matrimony, like in the days of Sodom and Gomorrah of Old.
Pacquiao, 33, claimed Obama's support for gay marriage, which the president proclaimed in a watershed moment for the country last week, was an attack on moral society, according to examiner.com.
Pacquiao, whose boxing nickname is Pac-Man after his last name, has weighed in on political issues before.
And since he became a congressman in the Philippines in 2010, it's part of his job.
Earlier this month, the star fighter said he opposed a Filipino bill to force the government to offer birth control and parenthood advice to its citizens.
Pacquiao cited his religious beliefs for his opposition.
God said, 'Go out and multiply.' He did not say, just have two or three kids, Pacquiao said, according to beatboxingmayhem.com. It is sinful to use condoms and commit abortion... my parents were poor... they had four children, it was very difficult but we persevered.
Pacquiao's relationship with God is so deep that he once said God told him in a dream to retire.
I will not stay long in boxing because he said: 'You have done enough. You have made yourself famous but this is harmful,' Pacquiao said at the time.
Yet his career continues as fans hope for the day the Pac-Man will fight Mayweather, arguably boxing's top two fighters.