I've watched enough porn that it doesn't register. I thought my original PFP was pretty tasteful, but it was still sexual, so I felt the need to get rid of it. I can accept many of the reasons people here give. The top two being..
1) Avatars are the same for the non sexual sections, so if you comment anywhere other than the porn section, people will inevitibely be forced to see it while reading the forums. My and your comfort with our bodies, and sexual desires don't have to be forced onto anyone. You don't post gay porn in the F/M section.
2) Not being taken seriously, with the possibility of bad intentions. I would like to be taken seriously as a zoo. A nude being the first thing is a bit much, unless it is all you are here for, and you are keeping your comments to the porn section.
My vote is everything or nothing..
The ultimatum would be seperate avatars for the the general chat/ mischevious areas, with zero favoritism towards the sex, or species depicted.