If you only knew how many times I pick against my own team during the regular season and get it thrown in my face!
I usually root for the underdog, and it definitely held true last year for the #12 Raiders. Brown had some recent playoff magic, too. Anything is possible during the playoffs and it's why they play the game. March Madness should teach you that.
Hard to separate head and heart. If your team is the low seed, it is still difficult to root against them to not pull off the 'upset'. Maybe some simply like/dislike one team more than another, regardless of their record. Risking a home is a ridiculous analogy.