He was referring to the fact that gay men have vastly higher rates of anal and colon cancer. This study may explain the "why" mechanism. They are literally screwing up the bacteria in their ass through sex/shoving stuff that doesn't belong in there.

The rate of anal cancer among MSM is seventeen times higher than among heterosexuals. src

These facts are hidden in CDC data and other places but cannot be discussed because nothing that shows any behavior or group as perceivably "inferior" can be talked about. You get wonderful pieces of idiocy like this instead.

tldr: slobber + rectum = ass cancer