A "maddowsexual" is a straight male, who watches MSNBC regularly because he thinks Rachel Maddow is hot, i.e., she is the object of his desire.
Guy 1: What did you do last night?
Guy 2: Watched MSNBC and had a maddowsexual moment. She's serious fap material when she tears into Pat Buchanan.
Of course, some people will disagree.
Guy 3: Dude, I think I'm a maddowsexual. I got so hot watching her last night.
Guy 4: TMI bro. Not with my dog's dick. You need to start watching Ann Coulter.