Rape by penis is potentially more harmful and invasive than rape by lips or fingers, seems to me...but it's clear that either experience would be quite unpleasant for the recipient in both a physical and a psychological sense. Nevertheless, the possibility or likelihood of such an assault by a man (gay or otherwise) is tremendously higher than it is by a woman...and everybody knows that. It's completely obvious. It's like saying "You are more likely to drown in water than in sand." (and you definitely can drown in either)

The very nature of male sexuality, by virtue of the physical structure of males, is more aggressive, while the nature of female sexuality, again by virtue of the physical structure itself, is more receptive (or passive). That doesn't prevent some individual females from being aggressive, of course, nor does it prevent some individual males from being passive, but it definitely does color the general nature of their sexual actions to a considerable extent.