There's no concrete proof, only suggestions and forced hints.
1) He says they couldn't make you sterile without removing whole penis in the 1970s. Right, and the AI or
Les Enfant Terriblescouldn't have been formed either.
2)Snake still recoves psyche from looking at the Playboy magazine. He still is turned on by women, but just a more focused soldier. It's also why he's hesitant about shooting the BnBs.
3) A large part of his rant just blows over removing the testicles because it makes for a more interesting article if you ignore it. Yet that one is the most likely and something the president could still check for in MGS2 quite easily.
4) Bulges. The only one there that doesn't have a bulge is the Nintendo one, one that Nintendo probably chose to reduce and is decidedly non-canon. The shadowy dark one was also on the PS1, back when Sony had decency standards to carefully watch on high profile titles.
5) This guy is crazy, referring to MPO as MGS
O, half-way suggesting Ghost Babel was canon and that MGS3 was a virtual mission because of the word 'virtuous.'
6) Then he retcons his own thing justifying the existence of Raiden's son as taking his sperm BEFORE they removed his penis and gave him artificial blood or some shit.