The All-American defensive end came out to his teammates at Missouri last August, but didn't inform his parents until last week.
Michael Sam Sr. said his son sent him a text message that said, "Dad, I'm gay."
The elder Sam told the New York Times that he was floored by the text.
"I couldn't eat no more, so I went to Applebee's to have drinks," Sam Sr. told the Times. "I don't want my grandkids raised in that kind of environment."
While he hopes his son makes it to the NFL, Sam Sr. made it clear that he's uncomfortable with the idea of an openly gay player competing in the league. Deacon Jones, the legendary former pass rusher, “is turning over in his grave,” Sam Sr. said.
“I’m old school,” Sam Sr. said, telling the Times that he took an older son to Mexico to lose his virginity. “I’m a man-and-a-woman type of guy.”
Some NFL insiders are uncomfortable with the news, too. After Michael Sam came out publicly on Sunday, nearly a dozen anonymous league executives said the announcement will likely hurt his prospects in this year's draft.
"I don't think football is ready for [an openly gay player] just yet," one NFL player personnel assistant told Sports Illustrated. "In the coming decade or two, it's going to be acceptable, but at this point in time it's still a man's-man game. To call somebody a [gay slur] is still so commonplace. It'd chemically imbalance an NFL locker room and meeting room."