Interesting dicotomy there. A man who flashes a known deeply christian man, Tom Landry, in his avatar and uses his words to form his signature attacks the "Great Commission" That Jesus came to proclaim! Irony or hypocrisy, you decide!
It is the role of all believers to use every opportunity to influence their sphere of influence to come to Christ. So do we expect our players to ignore their calling simply because the fans are non believers? I say not on your life. I wont even gratify those making half hearted jokes about the outcome of sporting events at the expense of God, but I do look forward to my eternity in the Kingdom of Heaven, my question is what about you? All things of this world are temperal, your eternity must always remain your priority, especially when you have the power of someone like Roy Williams to reach so many who cant find their way home.
As to Reggie White, to say that he "took back" his Praise for God after he left the field is to not understand the truth of what occurred. Reggie did not denounce his faith, nor did he stray from God. Reggie did something we ALL should do. He went to the Word of God and sought to understand what God meant for him to do. Even efforting to learn a new language to understand the scrolls and early writtings of those closest to Jesus. Reggie was on a crusade to be closer to God, not on a mission to detract from his creators kingdom!