This phrase is a way to make fun of people who say 'that's so gay' by changing it to 'that's so straight'. Many gay people (or people who think its offensive) use it instead of 'That's so gay' to show that its a hurtful phrase.
Amy: I got a ton of bio homework to do tonight, we can't go on our date...
Dane: Damn, that's so gay!
Amy: That isn't gay. That's so straight! (like you lol)
Dane: *crys in corner*
Fogey/fogy /fougi/ sl. (early 18C+, orig. Scot) old-fashioned, stuck-in-the mud.
Person with old fashioned ideas which he is unwilling to change: Come to the disco and stop being such an old fogey!
You think me an old fogeyand an old tory, his thoughtful voice said. I saw three generations since O’Connel’s time. I remember the famine. Do you know that the orange lodges agitated for repeal of the union twenty years before O’Connel did or before the prelates of your communion denounced him as a demagogue? You fenians forget some things. (James Joyce, Ulysses. Penguin Books,1992. p. 38)