How do I convince my son he is not gay?

I think you're being very stereotypical about gays wearing pink,and being manly, if a guy has a manly job that doesn't mean its impossible he is gay, If you think he may be confused about his sexuality then, you need to leave him to sort itself out. As you said You're usually a very open-minded Person, And maybe you need to be more open-minded about this.I respect the fact you never thought he would be gay, But you cant simply convince him he is not, If his feelings for men are strong then unfortunately there is nothing you can do, But is not up to you to choose his sexuality.~ I hope I helped :)