While we think of it as recreational, I assume it's a big deal to guys who can't get it up but want to have kids. It corrects a dysfunction.
Transsexual surgery, on the other hand, mutilates someone's body so that they can feel better about themselves.
While you can argue that taxpayer dollars shouldn't go to Viagra, there's a reasonable argument for it. There's no reasonable argument for the military to take on the added costs of sex surgeries. Otherwise, as I said, why stop there? Boob jobs, butt jobs, collagen implants, facelifts...you name it, taxpayers should pay for it (by your logic).
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*