Haha... Sigmond Freud ('s dead body) could prepare a thesis just from hearing the dudes on this site.
"Men are wery protective of vhat goes in zeir butts."
I wouldn't care about a finger stimulating my prostate as long as it is a girl's: God wouldn't put it there if he/she didn't want a girl poking it, although, for the guys who're slightly homophobic, you can put pressure on your prostate by, if jerkin' it, pushing your penis towards your feet, or if you're with a girl, for instance, being in the cowgirl position and having her lean back.