Losing your man card means allowing another man to masturbate himself to orgasm using your anus and rectum as a vagina, and to ejaculate his testicles inside your large intestine, mixing his semen with your fecal matter. (Every time you see a rainbow flag, that's what it stands for.)

Try to think of something more viscerally revolting.

You can't - and men who do this are OPENLY AND PROUDLY teaching it to little children in public schools, using explicit adult sex manuals.