Anal sex is riskier because during anal sex you actually create tiny tears in the Anal lining that can secrete blood. The anus is designed to push things out, not take things so you can understand why shoving things up there would be ill advised.
It's also why people pop pills in they anus. So They can be absorbed through the blood stream quicker. Causing a faster and better high.

idk why but your post made me think of this...
Suck my dikk it's the kid with the fat knob
I bust all into ya face, plus it come in globs
Quick get on your knees, with yo' sweet p*ssy let it breathe
Two fingers is all in your hole, think I can fit three
Your pink lips, spread it in shyt, let me throw my dikk in
Grab my shyt and place it gently, on your clit
Ping-pong p*ssy, wide world of wombs titty saggin
Stomach on some scriveled up prune shyt
Too much air in your p*ssy you screamin that it's
TALKIN TO YOU DADDY, fart's breathin out your lips splashin my dikk badly
Use vinegar, to try to tighten up your ginger
All-mighty dikk, ran in with a cape, some call him engine
Lightning rod bob, black candy cane attatched to God
Thick, like a great adventure cigar, in your garage
Pregnant p*ssy have you fall out, like Remi on the house
Watch the teeth for slobbin my shyt
You bit it on the couch, dry p*ssy leave the friction burns
Plus beef I hone, the condom broke
bytch you got AIDS I'm shakin in my bones